CHAPTER 187
Itching and Noninfectious Rashes
Itching and rashes may develop as the result of infection or irritation or from a reaction of the immune system. Some rashes occur mostly in children (see page 1734), whereas others almost always occur in adults. Sometimes an immune reaction is triggered by substances a person touches or eats, but many times doctors do not know why the immune system reacts to produce a rash.
The diagnosis of most noninfectious rashes is based on the appearance of the rash. The cause of a rash cannot be determined by blood tests, and tests of any kind are rarely performed. However, persistent rashes, particularly those that do not respond to treatment, may lead the doctor to perform a skin biopsy, in which a small piece of skin is surgically removed for examination under a microscope. Also, if the doctor suspects a contact allergy as the cause, skin tests may be performed (see page 1278).
Itching
Itching (pruritus) is a sensation that instinctively demands scratching.
Skin disorders, certain diseases, drugs, pregnancy, dry skin, contact with irritants, and scratching can cause itching.
Typical symptoms include dry skin, flaking, scaling, and visible insect bites.
The diagnosis is based on symptoms, allergy skin testing, blood tests, stoppage of drugs, or sometimes a biopsy or skin scraping.
Brief bathing in lukewarm water, moisturizers, antihistamines, corticosteroid creams, and certain types of drugs can relieve itching.
Itching may be caused by a skin disorder or by a disease that affects the whole body (systemic disease). Skin disorders that cause severe itching include infestations with parasites (such as scabies, mites, or lice), insect bites, hives, atopic dermatitis, and allergic dermatitis and contact dermatitis. These disorders usually also produce a rash. Systemic diseases that can cause itching include liver disease, kidney failure, lymphomas, leukemias and other blood disorders, and, occasionally, thyroid disease, diabetes, and cancer. However, itching from these diseases usually does not result in a rash.
Many drugs can cause itching, including barbiturates, morphine, and aspirin, as well as any drug to which a person has an allergy.
Itching is also common during the later months of pregnancy. Usually, pregnancy-related itching does not indicate any abnormality, but it can result from mild liver problems.
Often, contact with wool clothing or irritants, such as solvents or cosmetics, causes itching. Dry skin (xerosis), which is especially common among older people, can cause severe, widespread itching. Dry skin also can result from cold weather or prolonged exposure to water. Hot baths typically worsen itching.
The act of scratching can itself irritate the skin and lead to more itching, creating an itching-scratchingitching cycle. Vigorous scratching may cause redness and deep scrapes in the skin. In some people, even gentle scratching causes raised, red streaks that can itch intensely. Prolonged scratching and rubbing can thicken and scar the skin.
Diagnosis
Doctors try to determine the cause of itching to eliminate it. Often, the cause is obvious, such as an insect bite or poison ivy. Itching that lasts longer than a few days or that comes and goes frequently without an obvious cause usually requires testing. If an allergy is suspected, skin tests may be performed (see pages 1113 and 1278). If a systemic disease is suspected, blood tests are usually performed to check liver function, kidney function, and blood sugar levels. The number of eosinophils, a type of white blood cell, may be checked as well, because a high number may indicate an allergic reaction. Sometimes, the doctor may have a person discontinue one or more drugs to see whether the itching is relieved. A biopsy, in which a small piece of skin is surgically removed for examination under a microscope, or skin scraping (see page 1278) may help identify the cause, including an infectious one.
Treatment
For itching of any cause, bathing should be kept brief and preferably in cool or lukewarm water with very little or no soap. The skin should be patted dry gently rather than rubbed vigorously. Many people with itching benefit from an over-the-counter moisturizing cream applied right after bathing. The moisturizer should be odorless and colorless, because additives that provide color or scent may irritate the skin and may even cause itching. Fingernails, especially children’s, should be kept short to minimize abrasions from scratching. Coating the affected area with soothing compounds, such as menthol, camphor, chamomile, eucalyptus, or calamine, also may help.
When the Skin Is Dry
Normal skin owes its soft, pliable texture to its water content. To help protect against water loss, the outer layer of skin contains oil, which slows evaporation and holds moisture in the deeper layers of skin. If the oil is depleted, the skin becomes dry.
Dry skin (xerosis) is common, especially among people past middle age. Common causes are cold weather and frequent bathing. Bathing washes away surface oils, allowing the skin to dry out. Dry skin may become irritated and often itches—sometimes it sloughs off in small flakes and scales. Scaling most often affects the lower legs. Rubbing or scratching dry skin can lead to infection and scarring.
A form of severe dry skin is called ichthyosis. Ichthyosis can be an inherited disorder or can result from a number of other medical problems, such as an underactive thyroid gland, lymphoma, and AIDS.
The key to treating simple dry skin is keeping the skin moist. Taking fewer baths allows protective oils to remain on the skin. Moisturizing ointments or creams containing petroleum jelly, mineral oil, or glycerin also can hold water in the skin. Harsh soaps, detergents, and the perfumes in some moisturizers irritate the skin and may further dry it.
When scaling is a problem, solutions or creams containing salicylic or lactic acid or urea may help remove the scales. For some forms of severe ichthyosis, creams containing substances related to vitamin A, such as tretinoin, help the skin shed excessive scales.
Taking antihistamines by mouth may decrease itching. Some antihistamines, such as hydroxyzine and diphenhydramine, usually cause sleepiness and dry mouth and are mainly used at bedtime. Other antihistamines, such as loratadine and cetirizine, usually do not cause sleepiness. Generally, creams containing antihistamines (such as diphenhydramine) should not be used, because they themselves can cause an allergic reaction.
Corticosteroid creams decrease inflammation and control itching and may be used when itching is limited to a small area. Itching from some conditions, such as poison ivy, may require high-strength corticosteroid creams. However, only mild corticosteroids, such as 1% hydrocortisone, should be applied to the face, because stronger corticosteroids may thin the sensitive skin in this area. Also, powerful corticosteroid creams applied over large areas or for a long time can cause serious medical problems, especially in infants, because these drugs are absorbed into the bloodstream. Corticosteroids taken by mouth are sometimes used when large areas of the body are involved.
Specific treatments may be needed. For example, when fungal, parasitic, or bacterial infections cause itching, topical or systemic drugs may be required. Topical drugs are applied directly to the affected area of the skin. Systemic drugs are taken by mouth or are injected and are distributed throughout the body.
Dermatitis
Dermatitis (eczema) is inflammation of the upper layers of the skin, causing itching, blisters, redness, swelling, and often oozing, scabbing, and scaling.
Known causes include contact with a particular substance, certain drugs, varicose veins, constant scratching, and fungal infection.
Typical symptoms include a red itchy rash, blisters, pimples, open sores, oozing, crusting, and scaling.
The diagnosis is typically based on symptoms and confirmed by results of patch tests or skin samples or the presence of suspected drugs, irritants, or infection.
Avoiding known irritants and allergens reduces the risk of dermatitis.
Treatment depends on the cause and the specific symptoms.
Dermatitis is a broad term covering many different disorders that all result in a red, itchy rash. The term eczema is sometimes used for dermatitis. Some types of dermatitis affect only specific parts of the body, whereas others can occur anywhere. Some types of dermatitis have a known cause, whereas others do not. However, dermatitis is always the skin’s way of reacting to severe dryness, scratching, an irritating substance, or an allergen. Typically, that substance comes in direct contact with the skin, but sometimes the substance is swallowed. In all cases, continuous scratching and rubbing may eventually lead to thickening and hardening of the skin.
Dermatitis may be a brief reaction to a substance. In such cases, it may cause symptoms, such as itching and redness, for just a few hours or for only a day or two. Chronic dermatitis persists over a period of time. The hands and feet are particularly vulnerable to chronic dermatitis, because the hands are in frequent contact with many foreign substances and the feet are in the warm, moist conditions created by socks and shoes that favor fungal growth.
Chronic dermatitis may represent a contact, fungal, or other dermatitis that has been inadequately diagnosed or treated, or it may be one of several chronic skin disorders of unknown origin. Because chronic dermatitis produces cracks and blisters in the skin, any type of chronic dermatitis may lead to bacterial infection.
CONTACT DERMATITIS
Contact dermatitis is skin inflammation caused by direct contact with a particular substance. The rash is very itchy, is confined to a specific area, and often has clearly defined boundaries.
Substances can cause skin inflammation by one of two mechanisms—irritation (irritant contact dermatitis) or allergic reaction (allergic contact dermatitis).
Irritant contact dermatitis, which accounts for 80% of all cases of contact dermatitis, occurs when a chemical substance causes direct damage to the skin; symptoms are more painful than itchy. Typical irritating substances are acids, alkalis (such as drain cleaners), solvents (such as acetone in nail polish remover), strong soaps, and plants (such as poinsettias and peppers). Some of these chemicals cause skin changes within a few minutes, whereas others require longer exposure. People vary in the sensitivity of their skin to irritants. Even very mild soaps and detergents may irritate the skin of some people after frequent or prolonged contact.
Allergic contact dermatitis is a reaction by the body’s immune system to a substance contacting the skin. Sometimes a person can be sensitized by only one exposure, and other times sensitization occurs only after many exposures to a substance. After a person is sensitized, the next exposure causes itching and dermatitis within 4 to 24 hours, although some people, particularly older people, do not develop a reaction for 3 to 4 days.
Thousands of substances can result in allergic contact dermatitis. The most common include substances found in plants such as poison ivy, rubber (latex), antibiotics, fragrances, preservatives, and some metals (such as nickel and cobalt). About 10% of women are allergic to nickel, a common component of jewelry. People may use (or be exposed to) substances for years without a problem, then suddenly develop an allergic reaction. Even ointments, creams, and lotions used to treat dermatitis can cause such a reaction. People may also develop dermatitis from many of the materials they touch while at work (occupational dermatitis).
Sometimes contact dermatitis results only after a person touches certain substances and then exposes the skin to sunlight (photoallergic or phototoxic contact dermatitis). Such substances include sunscreens, aftershave lotions, certain perfumes, antibiotics, coal tar, and oils.
Symptoms and Diagnosis
Regardless of cause or type, contact dermatitis results in itching and a rash. The itching is usually severe, but the rash varies from a mild, short-lived redness to severe swelling and large blisters. Most commonly, the rash contains tiny blisters. The rash develops only in areas contacted by the substance. However, the rash appears earlier in thin, sensitive areas of skin, and later in areas of thicker skin or on skin that had less contact with the substance, giving the impression that the rash has spread. Touching the rash or blister fluid cannot spread contact dermatitis to other people or to other parts of the body that did not make contact with the substance.
Common Causes of Allergic Contact Dermatitis
Cosmetics: Hair-removing chemicals, hair dyes, nail polish, nail polish remover, deodorants, moisturizers, aftershave lotions, perfumes, sunscreens
Metal compound (in jewelry): Nickel
Plants: Poison ivy, poison oak, poison sumac, ragweed, primrose, thistle
Drugs in skin creams: Antibiotics (sulfonamides, neomycin), antihistamines (diphenhydramine, promethazine), anesthetics (benzocaine), antiseptics (thimerosal), stabilizers
Chemicals used in clothing manufacturing: Tanning agents in shoes; rubber accelerators and antioxidants in gloves, shoes, undergarments, other apparel
Determining the cause of contact dermatitis is not always easy. The person’s occupation, hobbies, household duties, vacations, clothing, topical drug use, cosmetics, and household members’ activities must be considered. Most people are unaware of all the substances that touch their skin. Often, the location of the initial rash is an important clue, particularly if it occurs under an item of clothing or jewelry or only in areas exposed to sunlight. However, many substances that people touch with their hands are unknowingly transferred to the face, where the more sensitive facial skin may react even if the hands do not.
The “use test,” in which a suspected substance is applied far from the original area of contact dermatitis (usually on the forearm), is useful when perfumes, shampoos, or other substances used in the home are suspected.
If a doctor suspects contact dermatitis and a process of elimination does not pinpoint the cause, patch testing can be performed. For this test, small patches containing substances that commonly cause dermatitis are placed on the skin for 1 to 2 days to see whether a rash develops beneath one of them. Although useful, patch testing is complicated. People may be sensitive to many substances, and the substance they react to on a patch may not be the cause of their dermatitis. A doctor must decide which substances to test based on what a person might have been exposed to.
Poison Ivy Dermatitis
About 50 to 70% of people are sensitive to the plant oil urushiol contained in poison ivy, poison oak, and poison sumac. Similar oils are also present in the shells of cashew nuts; the leaves, sap, and fruit skin of the mango; and Japanese lacquer. Once a person has been sensitized by contact with these oils, subsequent exposure produces a contact dermatitis.
The oils are quickly absorbed into the skin but may remain active on clothing, tools, and pet fur for long periods of time. Smoke from burning plants also contains the oil and may cause a reaction in certain people. Sensitivity to poison ivy tends to run in families.
Symptoms begin 8 to 48 hours after contact and consist of intense itching, a red rash, and multiple blisters, which may be tiny or very large. Typically, the blisters occur in a straight line following the track where the plant brushed along the skin. The rash may appear at different times in different locations either because of repeat contact with contaminated clothing and other objects or because some parts of the skin are more sensitive than others. The blister fluid itself is not contagious. The itching and rash last for 2 to 3 weeks.
Recognition and avoidance of contact with the plants is the best prevention. A number of commercial barrier creams and lotions can be applied before exposure to minimize, but not completely prevent, absorption of oil by the skin. The oil can soak through latex rubber gloves. Washing the skin with soap and water prevents absorption of the oil if done immediately. Stronger solvents, such as acetone, alcohol, and various commercial products, are probably no more effective. Desensitization with various shots or pills or by eating poison ivy leaves is not effective.
Treatment helps relieve symptoms but does not shorten the duration of the rash. The most effective treatment is with corticosteroids. Small areas of rash are treated with strong topical corticosteroids (drugs applied to the skin), such as triamcinolone, clobetasol, or diflorasone—except on the face and genitals, where only mild corticosteroids, such as 1% hydrocortisone, should be applied. People with large areas of rash or significant facial swelling are given high-dose corticosteroids taken by mouth. Cool compresses wet with water or aluminum acetate may be used on large blistered areas. Antihistamines given by mouth may help with itching. Lotions and creams containing antihistamines are seldom used.
Prevention and Treatment
Contact dermatitis can be prevented by avoiding contact with the causative substance. If contact does occur, the material should be washed off immediately with soap and water. If circumstances risk ongoing exposure, gloves and protective clothing may be helpful. Barrier creams are also available that can block certain substances, such as poison ivy and epoxy resins, from contacting the skin. Desensitization with injections or tablets of the causative substance is not effective in preventing contact dermatitis.
Treatment is not effective until there is no further contact with the substance causing the problem. Once the substance is removed, the redness usually disappears after a week. Blisters may continue to ooze and form crusts, but they soon dry. Residual scaling, itching, and temporary thickening of the skin may last for days or weeks.
Itching can be relieved with a number of topical drugs or drugs taken by mouth (see page 1283). In addition, small areas of dermatitis can be soothed by applying pieces of gauze or thin cloth dipped in cool water or aluminum acetate (Burow’s solution) several times a day for an hour. Larger areas may be treated with short, cool tub baths with or without colloidal oatmeal. The doctor may drain fluid from a large blister, but the blister is not removed.
ATOPIC DERMATITIS
Atopic dermatitis is chronic, itchy inflammation of the upper layers of the skin that often develops in people who have hay fever or asthma and in people who have family members with these conditions.
Atopic dermatitis is one of the most common skin diseases, affecting between 9% and 30% of children or adolescents in the United States. Almost 66% of people with the disorder develop it before age 1, and 90% by age 5. In half of these people, the disorder will be gone by the adolescent years, whereas in others it is lifelong.
Doctors do not know what causes atopic dermatitis, but people who have it usually have many allergic disorders, particularly asthma, hay fever, and food allergies. The relationship between the dermatitis and these disorders is not clear because atopic dermatitis is not an allergy to a particular substance. Atopic dermatitis is not contagious.
Many conditions can make atopic dermatitis worse, including emotional stress, changes in temperature or humidity, bacterial skin infections, and contact with irritating clothing (especially wool). In some infants, food allergies may provoke atopic dermatitis.
Symptoms
Infants may develop red, oozing, crusted rashes on the face, scalp, diaper area, hands, arms, feet, or legs. Large areas of the body may be affected. In older children and adults, the rash often occurs (and recurs) in only one or a few spots, especially on the hands, upper arms, in front of the elbows, or behind the knees.
Although the color, intensity, and location of the rash vary, the rash always itches. The itching often leads to uncontrollable scratching, triggering a cycle of itching-scratching-itching that makes the problem worse. Scratching and rubbing can also tear the skin, leaving an opening for bacteria to enter and cause infections.
In people with atopic dermatitis, infection with the herpes simplex virus, which in other people usually affects a small area with tiny, slightly painful blisters (see page 1245), may produce a serious illness with widespread dermatitis, blistering, and high fever (eczema herpeticum).
Diagnosis and Treatment
A doctor makes the diagnosis based on the typical pattern of the rash and often on whether other family members have allergies.
No cure exists, but itching can be relieved with topical drugs or drugs taken by mouth (see page 1283). Certain other measures can help. Avoiding contact with substances known to irritate the skin or foods that the person is sensitive to can prevent a rash. The skin should be kept moist, either with commercial moisturizers or with petroleum jelly or vegetable oil. Moisturizers are best applied immediately after bathing, while the skin is damp.
Specific treatments include applying a corticosteroid ointment or cream. To limit the use of corticosteroids in people being treated for long periods, doctors sometimes replace the corticosteroids with petroleum jelly for a week or more at a time. Ointments or creams containing an immune system-modulating drug, such as tacrolimus or pimecrolimus, also are helpful and can limit the need for long-term corticosteroid use. Some doctors prescribe such drugs first. Corticosteroid tablets are a last resort for people with stubborn cases.
Phototherapy (exposure to ultraviolet light) may help adults (see box on page 1294). This treatment is rarely recommended for children because of its potential long-term side effects, including skin cancer and cataracts.
For severe cases, the immune system can be suppressed with cyclosporine, azathioprine, or mycophenolate mofetil taken by mouth, or injections of interferon-gamma.
SEBORRHEIC DERMATITIS
Seborrheic dermatitis is chronic inflammation that causes yellow, greasy scales to form on the scalp and face and occasionally on other areas.
The cause is unknown. Seborrheic dermatitis occurs most often in infants, usually within the first 3 months of life, and in those aged 30 to 70 years. The disorder is more common among men, often runs in families, and is worse in cold weather. A form of seborrheic dermatitis also occurs in as many as 85% of people with AIDS.
Symptoms
Seborrheic dermatitis usually begins gradually, causing dry or greasy scaling of the scalp (dandruff), sometimes with itching but without hair loss. In more severe cases, yellowish to reddish scaly pimples appear along the hairline, behind the ears, in the ear canal, on the eyebrows, on the bridge of the nose, around the nose, on the chest, and on the upper back. In infants younger than 1 month of age, seborrheic dermatitis may produce a thick, yellow, crusted scalp rash (cradle cap) and sometimes yellow scaling behind the ears and red pimples on the face. Frequently, a stubborn diaper rash accompanies the scalp rash. Older children and adults may develop a thick, tenacious, scaly rash with large flakes of skin.
Treatment
The scalp can be treated with a shampoo containing pyrithione zinc, selenium sulfide, an antifungal drug, salicylic acid and sulfur, or tar. The person usually uses the medicated shampoo every other day until the dermatitis is controlled and then twice weekly. Ketoconazole cream is often effective as well. In adults, thick crusts and scales, if present, can be loosened with overnight application of corticosteroids or salicylic acid under a shower cap.
Often, treatment must be continued for many weeks. If the dermatitis returns after the treatment is discontinued, treatment can be restarted. Topical corticosteroids are also used on the head and other affected areas. On the face, only mild corticosteroids, such as 1% hydrocortisone, should be used. Even mild corticosteroids must be used cautiously, because long-term use can thin the skin and cause other problems.
In infants and young children who have a thick scaly rash on the scalp, 2% salicylic acid in mineral oil can be rubbed gently into the rash with a soft toothbrush at bedtime. The scalp can also be shampooed daily with mild baby shampoo, and 1% hydrocortisone cream can be rubbed into the scalp.
NUMMULAR DERMATITIS
Nummular dermatitis is a persistent, usually itchy, rash and inflammation characterized by coin-shaped spots, often with tiny blisters, scabs, and scales.
The cause is unknown. Nummular dermatitis usually affects middle-aged people, occurs along with dry skin, and is most common in winter. However, the rash may come and go without any apparent reason.
The round spots start as itchy patches of pimples and blisters that later ooze and form crusts. The rash may be widespread. Often, spots are more obvious on the backs of the arms or legs and on the buttocks, but they also appear on the torso.
Most people benefit from skin moisturizers. Other treatments include antibiotics taken by mouth, corticosteroid creams and injections, and phototherapy (exposure to ultraviolet light). All treatments, however, are often unsatisfactory.
GENERALIZED EXFOLIATIVE DERMATITIS
Generalized exfoliative dermatitis (erythroderma) is severe inflammation that causes the entire skin surface to become red, cracked, and covered with scales.
Certain drugs (especially penicillins, sulfonamides, isoniazid, phenytoin, and barbiturates) may cause this disorder. In some cases, it is a complication of other skin diseases, such as atopic dermatitis, psoriasis, and contact dermatitis. Certain lymphomas (cancers of the lymph nodes) may also cause generalized exfoliative dermatitis. In many cases, the cause is unknown.
Symptoms and Diagnosis
Exfoliative dermatitis may start rapidly or slowly. At first the entire skin surface becomes red and shiny. Then the skin becomes scaly, thickened, and sometimes crusted. Sometimes the hair and nails fall out. Some people have itching and swollen lymph nodes. Although many people have a fever, they may feel cold and have chills because so much heat is lost through the damaged skin. Large amounts of fluid and protein may seep out, and the damaged skin is a poor barrier against infection.
Because symptoms of exfoliative dermatitis are similar to those of skin infection, doctors send samples of skin and blood to the laboratory to exclude infection as a cause.
Treatment
Early diagnosis and treatment are important in preventing infection from developing in the affected skin and in keeping fluid and protein loss from becoming life threatening.
People with severe exfoliative dermatitis often need to be hospitalized and given antibiotics (for infection), intravenous fluids (to replace the fluids lost through the skin), and nutritional supplements. Care may include the use of drugs and heated blankets to control body temperature. Cool baths followed by applications of petroleum jelly and gauze may help protect the skin. Corticosteroids (such as prednisone) given by mouth or intravenously are used only when other measures are unsuccessful or the disease worsens. Any drug or chemical that could be causing the dermatitis should be eliminated. If lymphoma is causing the dermatitis, treatment of the lymphoma is helpful.
STASIS DERMATITIS
Stasis dermatitis is inflammation on the lower legs from pooling of blood and fluid.
Stasis dermatitis tends to occur in people who have varicose (dilated, twisted) veins (see page 437) and swelling (edema). It usually occurs on the ankles but may spread upward to the knees. At first, the skin becomes reddened and mildly scaly. Over several weeks or months, the skin turns dark brown. Eventually, areas of the skin may break down and form an open sore (ulcer), typically near the ankle. Ulcers sometimes become infected with bacteria. Stasis dermatitis makes the legs feel itchy and swollen, but not painful. Ulcers are usually painful.
Treatment
Long-term treatment is aimed at keeping blood from pooling in the veins around the ankles. When sitting, the person should elevate the legs above the level of the heart. Properly fitted prescription support hose (compression stockings) also prevent pooling of blood and decrease swelling. Department store “support” stockings are not adequate.
For dermatitis of recent onset, soothing compresses, such as gauze pads soaked in tap water or aluminum acetate (Burow’s solution), may make the skin feel better and can help prevent infection by keeping the skin clean. If the disorder worsens, as evidenced by increased warmth, redness, small ulcers, or pus, a more absorbent dressing can be used. Corticosteroid creams are also helpful and are often combined with zinc oxide paste and applied in a thin layer. Corticosteroids should not be applied directly to an ulcer because this will interfere with healing.
When a person has large or extensive ulcers, special moisture-containing hydrocolloid or hydrogel dressings may be used. Antibiotics are used only when the skin is already infected. Sometimes, skin from elsewhere on the body may be grafted to cover very large ulcers.
Some people may need an Unna’s paste boot, which is a woven stretch wrap filled with a gelatin paste that contains zinc. The wrap is applied to the ankle and lower leg where it hardens, similar to but softer than a cast. The boot limits swelling and helps protect the skin from irritation, and the paste helps heal the skin. At first the boot is changed every 2 or 3 days, but later it is left on for a week at a time. After the ulcer heals, an elastic support should be applied before the person rises in the morning. Regardless of the dressing used, reduction of swelling (usually with compression) is essential for healing.
In stasis dermatitis, the skin is easily irritated. Antibiotic creams, first-aid (anesthetic) creams, alcohol, witch hazel, lanolin, or other chemicals should not be used because they can make the disorder worse.
LOCALIZED SCRATCH DERMATITIS
Localized scratch dermatitis (lichen simplex chronicus, neurodermatitis) is chronic, itchy inflammation of the top layer of the skin.
Localized scratch dermatitis is caused by chronic scratching of an area of skin. The act of scratching triggers more itching, beginning a vicious circle of itching-scratching-itching. Sometimes the scratching begins for no apparent reason. Other times scratching starts because of a contact dermatitis, parasitic infestation, or other condition, but the person continues to scratch long after the inciting cause is gone. Doctors do not know why this happens, but psychologic factors may play a role. The disorder does not seem to be allergic. More women than men have localized scratch dermatitis, and it is common among Asians and Native Americans. It usually develops between the ages of 20 and 50.
Symptoms and Diagnosis
Localized scratch dermatitis can occur anywhere on the body, including the anus (pruritus ani—see page 183) and the vagina (pruritus vulvae—see page 1500), but is most common on the head, arms, and legs. In the early stages, the skin looks normal, but it itches. Later, dryness, scaling, and dark patches develop as a result of the scratching and rubbing.
Doctors try to discover any possible underlying allergies or diseases that may be causing the initial itching. When the disorder occurs around the anus or vagina, the doctor may investigate the possibility of pinworms, trichomoniasis, hemorrhoids, local discharges, fungal infections, warts, contact dermatitis, or psoriasis as the cause.
Treatment
For the disorder to clear up, the person must stop all scratching and rubbing of the area. Standard treatments for itching should be followed (see page 1283). Applying surgical tape saturated with a corticosteroid (applied in the morning and replaced in the evening) helps relieve itching and inflammation and protects the skin from scratching. The doctor may inject longer-acting corticosteroids under the skin to control the itching.
When this disorder develops around the anus or vagina, the best treatment is a corticosteroid cream. Zinc oxide paste may be applied over the cream to protect the area. This paste can be removed with mineral oil.
PERIORAL DERMATITIS
Perioral dermatitis is a red, bumpy rash around the mouth and on the chin that resembles acne or rosacea.
The disorder, whose cause is unknown, mainly affects women between the ages of 20 and 60. Perioral dermatitis is distinguished from acne by the lack of blackheads and whiteheads (comedones). Perioral dermatitis can be hard to separate from rosacea, but symptoms, including tiny blisters and skin scaling, can help make the distinction. Other symptoms of rosacea must be present for that diagnosis to be made instead of perioral dermatitis.
Treatment is with tetracyclines or other antibiotics taken by mouth. If these antibiotics do not clear up the rash and the disorder is particularly severe, isotretinoin, an acne drug, may help. Corticosteroids and some oily cosmetics, especially moisturizers, tend to worsen the disorder.
POMPHOLYX
Pompholyx is a chronic dermatitis characterized by itchy blisters on the palms and sides of the fingers and sometimes on the soles of the feet.
Pompholyx is sometimes called dyshidrosis, which means “abnormal sweating,” but the disorder has nothing to do with sweating. Doctors do not know what causes pompholyx, but fungal infection, contact dermatitis, or stress may be a factor as well as some ingested substances such as nickel, chromium, and cobalt. It is more common among adolescents and young adults.
The blisters are often scaly, red, and oozing. Pompholyx comes and goes in attacks that last 2 to 3 weeks. Pompholyx takes weeks to go away on its own. Wet compresses with potassium permanganate or aluminum acetate (Burow’s solution) may help the blisters resolve. Strong topical corticosteroids, tacrolimus, or pimecrolimus may help itching and inflammation. Pompholyx can also be treated with antibiotics taken by mouth and with phototherapy.
Drug Rashes
Drug rashes are a side effect of a drug that manifests as a skin reaction.
Drug rashes usually are caused by an allergic reaction to a drug.
Typical symptoms include mild redness, peeling, hives, and others, such as a runny nose and watery eyes.
Every drug a person takes is stopped to figure out which one is causing the rash.
Most drug rashes resolve with the withdrawal of the drug; however, serious reactions require injections of epinephrine, diphenhydramine, and a corticosteroid.
Most drug rashes result from an allergic reaction to the drug (see page 96). The drug does not have to be applied to the skin to cause a drug rash. Sometimes a person can be sensitized to a drug by one exposure, and other times sensitization occurs only after many exposures to a substance. Later exposure to the drug may trigger an allergic reaction, such as a rash.
Sometimes a rash develops directly without involving an allergic reaction. For example, corticosteroids and lithium produce a rash that looks like acne, and anticoagulants (blood thinners) may cause bruising when blood leaks under the skin. Other important nonallergic rashes that may result from drugs are those that occur in Stevens-Johnson syndrome, toxic epidermal necrolysis, and erythema nodosum.
Certain drugs make the skin particularly sensitive to the effects of sunlight (photosensitivity). These drugs include certain antipsychotics, tetracycline, sulfa antibiotics, chlorothiazide, and some artificial sweeteners. No rash appears when the drug is taken, but later exposure to the sun produces a reddened area of skin that is sometimes itchy or that appears grayish blue.
Symptoms
Drug rashes vary in severity from mild redness with tiny bumps over a small area to peeling of the entire skin. Rashes may appear suddenly within minutes after a person takes a drug, or they may be delayed for hours or days. People with an allergic rash often have other allergic symptoms—runny nose, watery eyes, wheezing, and even collapse from dangerously low blood pressure. Hives are very itchy (see page 1122), whereas other drug rashes itch little, if at all.
Diagnosis and Treatment
Figuring out whether a drug is responsible may be difficult because a rash can result from only a minute amount of a drug, it can erupt long after a person has taken a drug, and it can persist for weeks or months after a person has discontinued a drug. Every drug a person has taken is suspect, including those bought without a prescription—even eye drops, nose drops, and suppositories are possible causes. Sometimes the only way to determine which drug is causing a rash is to have the person discontinue all but life-sustaining drugs. Whenever possible, chemically unrelated drugs are substituted. If there are no such substitutes, the person starts taking the drugs again one at a time to see which one causes the reaction. However, this method can be hazardous if the person has had a severe allergic reaction to the drug. Skin testing is not helpful, except when penicillin is the suspected drug.
Most drug reactions disappear when the responsible drug is discontinued. Standard itching treatments are used as needed (see page 1283). Serious allergic eruptions, particularly those accompanied by significant symptoms such as wheezing or difficulty breathing, are treated with injections of epinephrine, diphenhydramine, and a corticosteroid.
Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis
Stevens-Johnson syndrome and toxic epidermal necrolysis are two forms of the same life-threatening skin disease that cause rash, skin peeling, and sores on the mucous membranes.
Stevens-Johnson syndrome and toxic epidermal necrolysis usually are caused by drugs or a bacterial infection.
Typical symptoms for both diseases include fever, body aches, a flat red rash, blisters that break out on the mucous membranes, and small areas of peeling skin (Stevens-Johnson syndrome) or large areas of peeling skin (toxic epidermal necrolysis).
Affected people are hospitalized in a burn unit, given fluids and sometimes corticosteroids and antibiotics, and all suspected drugs are stopped.
In Stevens-Johnson syndrome, a person has blistering of mucous membranes, typically in the mouth, eyes, and vagina, and patchy areas of rash. In toxic epidermal necrolysis, there is a similar blistering of mucous membranes, but in addition the entire top layer of the skin (the epidermis) peels off in sheets from large areas of the body. Both disorders can be life threatening.
Nearly all cases are caused by a reaction to a drug, most often sulfa antibiotics; barbiturates; anticonvulsants, such as phenytoin and carbamazepine; certain nonsteroidal anti-inflammatory drugs (NSAIDs); or allopurinol. Some cases are caused by a bacterial infection. Occasionally, a cause cannot be identified. The disorder occurs in all age groups but is more common among older people, probably because older people tend to use more drugs. The disorder is also more likely to occur in people with AIDS.
Symptoms
Stevens-Johnson syndrome and toxic epidermal necrolysis usually begin with fever, headache, cough, and body aches. Then a flat red rash breaks out on the face and trunk, often spreading later to the rest of the body in an irregular pattern. The areas of rash enlarge and spread, often forming blisters in their center. The skin of the blisters is very loose and easy to rub off. In Stevens-Johnson syndrome, less than 10% of the body surface is affected. In toxic epidermal necrolysis, large areas of skin peel off, often with just a gentle touch or pull. In many people with toxic epidermal necrolysis, 30% or more of the body surface peels away. The affected areas of skin are painful, and the person feels very ill with chills and fever. In some people, the hair and nails fall out. The active stage of rash and skin loss can last between 1 day and 14 days.
In both disorders, blisters break out on the mucous membranes lining the mouth, throat, anus, genitals, and eyes. The damage to the lining of the mouth makes eating difficult, and closing the mouth may be painful, so the person may drool. The eyes may become very painful, swell, and become so filled with pus that they seal shut. The corneas can become scarred. The opening through which urine passes (urethra) may also be affected, making urination difficult and painful. Sometimes the mucous membranes of the digestive and respiratory tracts are involved, resulting in diarrhea and difficulty breathing.
The skin loss in toxic epidermal necrolysis is similar to a severe burn and is equally life threatening. Huge amounts of fluids and salts can seep from the large, raw, damaged areas. A person who has this disorder is very susceptible to organ failure and infection at the sites of damaged, exposed tissues. Such infections are the most common cause of death in people with this disorder.
Treatment
People with Stevens-Johnson syndrome or toxic epidermal necrolysis are hospitalized. Any drugs suspected of causing the disorder are immediately discontinued. When possible, people are treated in a burn unit and given scrupulous care to avoid infection. If the person survives, the skin grows back on its own, and unlike burns, skin grafts are not needed. Fluids and salts, which are lost through the damaged skin, are replaced intravenously.
Use of corticosteroids to treat the disorder is controversial. Some doctors believe that giving large doses within the first few days is beneficial, whereas others believe that corticosteroids should not be used. These drugs suppress the immune system, which increases the potential for serious infection. If infection develops, doctors give antibiotics immediately.
In many cases, doctors give intravenous human immunoglobulin to treat toxic epidermal necrolysis. This substance helps to prevent further immune damage to the skin and further progression of blistering.
Erythema Multiforme
Erythema multiforme is a recurring disorder characterized by patches of red, raised skin that often look like targets and usually are distributed symmetrically over the body.
Erythema multiforme can be caused by a reaction to an infection with herpes simplex virus.
Typical symptoms include red patches with purple-gray centers (target lesions) that suddenly appear on arms, legs, face, palms, and soles and on the body.
The diagnosis is based on symptoms.
This disorder resolves without treatment, but symptoms can be treated with corticosteroids, lidocaine, and sometimes acyclovir.
Most cases are caused by a reaction to infection with the herpes simplex virus (see page 1245). This viral infection is apparent as visible cold sores in about two thirds of people before the erythema multiforme appears. Doctors are not sure whether other infectious diseases cause a few cases of erythema multiforme. Doctors are unsure exactly how herpes simplex causes this disorder, but a type of immune reaction is suspected.
Symptoms
Usually, erythema multiforme appears suddenly, with reddened patches erupting on the arms, legs, and face. Sometimes the rash is also present on the palms or soles. The red patches are distributed equally on both sides of the body. These red patches often develop red concentric rings with purple-gray centers (“target” or “iris” lesions) and small blisters. The reddened areas usually are symptomless, although they sometimes itch mildly. Painful blisters often form on the lips and lining of the mouth but not the eyes.
Attacks of erythema multiforme may last 2 to 4 weeks. Some people have only one attack, but some have recurrences an average of 6 times a year for almost 10 years. Recurrences are more common in the spring and can probably be triggered by sunlight. The frequency of recurrence usually decreases with time.
Diagnosis and Treatment
Doctors diagnose erythema multiforme by its characteristic appearance. However, Stevens-Johnson syndrome (see page 1290) may at first look very similar to erythema multiforme, so doctors monitor the person carefully until the diagnosis is clear.
Erythema multiforme resolves on its own. If itching is bothersome, standard treatments may be used. Corticosteroids given by mouth may be helpful. If painful mouth blisters make eating difficult, a topical anesthetic (an anesthetic applied to the skin), such as lidocaine, may be applied. If oral intake is still poor, nutrition and fluids are given intravenously. People with frequent recurrences may benefit from an antiviral drug, such as acyclovir, given at the first sign of an outbreak.
Erythema Nodosum
Erythema nodosum is an inflammatory disorder that produces tender red bumps (nodules) under the skin, most often over the shins but occasionally on the arms and other areas.
Erythema nodosum usually is caused by another disease, drug sensitivity, or bacterial, fungal, or viral infection.
Typical symptoms include fever, joint pain, and characteristic painful red bumps and bruises on the person’s shins.
The diagnosis is based on symptoms and supported by results of a chest x-ray, blood tests, and a biopsy.
People stop taking suspected drugs; underlying infections are treated with antibiotics; and pain is relieved by bed rest, nonsteroidal anti-inflammatory drugs, and sometimes an injection of a corticosteroid.
Quite often, erythema nodosum is a symptom of some other disease or of sensitivity to a drug. Young adults, particularly women, are most prone to the disorder, which may recur for months or years. Bacterial, fungal, or viral infections may also cause erythema nodosum.
Streptococcal infection is one of the most common causes of erythema nodosum, particularly in children. Sarcoidosis, ulcerative colitis, and various drugs, such as sulfa antibiotics and oral contraceptives, are other common causes. Numerous other infections and several types of cancer are also thought to cause the eruption.
Erythema nodosum nodules usually appear on the shins and resemble raised bumps and bruises that gradually change from pink to bluish brown. Fever and joint pain are common. Lymph nodes in the chest occasionally become enlarged and are detected with a chest x-ray. The painful nodules are usually the telltale sign for the doctor. Evaluation includes chest x-ray, blood tests, and skin biopsy, in which a small piece of skin is surgically removed for examination under a microscope.
Treatment
Drugs that might be causing erythema nodosum are discontinued, and any underlying infections are treated. If the disorder is caused by a streptococcal infection, a person may have to take antibiotics, such as penicillin, or a cephalosporin.
The nodules may go away in 3 to 6 weeks without treatment. Bed rest and nonsteroidal anti-inflammatory drugs (NSAIDs) may help relieve the pain caused by the nodules. Individual nodules may also be treated by injecting them with a corticosteroid. When a person has many nodules, corticosteroid or potassium iodide tablets sometimes are prescribed to speed relief of pain.
Granuloma Annulare
Granuloma annulare is a chronic, harmless skin disorder of unknown cause in which small, firm, raised bumps form a ring with normal or slightly sunken skin in the center.
The bumps are red, violet, or flesh-colored, and a person may have one ring or several. The bumps usually cause no pain or itching and they most often form on the feet, legs, hands, or fingers of children and adults. In a few people, clusters of granuloma annulare bumps erupt when the skin is exposed to the sun.
Most often, granuloma annulare heals without any treatment. Corticosteroid creams under waterproof bandages, surgical tape saturated with a corticosteroid, or injected corticosteroids may help clear up the rash. People with large affected areas often benefit from treatment that combines phototherapy (exposure to ultraviolet light) with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light). This treatment is called PUVA (psoralens plus ultraviolet A).
Psoriasis
Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin.
A problem with the immune system may play a role.
Characteristic scales appear on various parts of the body in large or small patches.
This disease is treated with a combination of exposure to ultraviolet light (phototherapy) and drugs applied to the skin and taken by mouth.
The patches of psoriasis occur because of an abnormally high rate of growth of skin cells. The reason for the rapid cell growth is unknown, but a problem with the immune system is thought to play a role. The disorder often runs in families. Psoriasis is common and affects about 1 to 5% of the population worldwide. Light-skinned people are at greater risk, whereas blacks are less likely to get the disease.
Symptoms
Psoriasis begins most often in people aged 10 to 40, although people in all age groups are susceptible.
It usually starts as one or more small patches on the scalp, elbows, knees, back, or buttocks. The first patches may clear up after a few months or remain, sometimes growing together to form larger patches. Some people never have more than one or two small patches, and others have patches covering large areas of the body. Thick patches or patches on the palms of the hands, soles of the feet, or skinfolds of the genitals are more likely to itch or hurt, but many times the person has no symptoms. Although the patches do not cause extreme physical discomfort, they are very obvious and often embarrassing to the person. The psychologic distress caused by psoriasis can be severe. Many people with psoriasis may also have deformed, thickened, and pitted nails.
Psoriasis persists throughout life but may come and go. Symptoms are often diminished during the summer when the skin is exposed to bright sunlight. Some people may go for years between occurrences. Psoriasis may flare up for no apparent reason or as a result of a variety of circumstances. Flare-ups often result from conditions that irritate the skin, such as minor injuries and severe sunburn. Sometimes flare-ups follow infections, such as colds and strep throat. Flare-ups are more common in the winter and after stressful situations. Many drugs, such as antimalarial drugs, lithium, and beta-blockers, can also cause psoriasis to flare up.
Some uncommon types of psoriasis can have more serious effects. Psoriatic arthritis produces joint pain and swelling (see page 569). Erythrodermic psoriasis causes all of the skin on the body to become red and scaly. This form of psoriasis is serious because, like a burn, it keeps the skin from serving as a protective barrier against injury and infection. In another uncommon form of psoriasis, pustular psoriasis, large and small pus-filled blisters (pustules) form on the palms of the hands and soles of the feet. Sometimes, these pustules are scattered on the body.
Treatment
Many drugs are available to treat psoriasis. Most often, a combination of drugs is used, depending on the severity and extent of the person’s symptoms.
Topical Drugs: Topical drugs (drugs applied to the skin) are used most commonly. Nearly everyone with psoriasis benefits from skin moisturizers (emollients). Other topical agents include corticosteroids, often used together with calcipotriene, a vitamin D derivative, or coal tar or pine tar. Tazarotene or anthralin may also be used. Very thick patches can be thinned with ointments containing salicylic acid, which make the other drugs more effective. Many of these drugs are irritating to the skin, and doctors must find which ones work best for each person.
Phototherapy: Phototherapy (exposure to ultraviolet light) also can help clear up psoriasis for several months at a time. Phototherapy is often used in combination with various topical drugs, particularly when large areas of skin are involved. Traditionally, treatment has been with phototherapy combined with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light). This treatment is called PUVA (psoralens plus ultraviolet A). Some doctors are now using narrow-band ultraviolet B (UVB) treatments, which are equally effective but avoid the need to use psoralens and the side effects they cause, such as extreme sensitivity to sunshine.
Oral Drugs: For serious forms of psoriasis and psoriatic arthritis, drugs taken by mouth are used. These drugs include cyclosporine, methotrexate, and acitretin. Cyclosporine is an immunosuppressant drug that may cause high blood pressure and damage the kidneys. Methotrexate interferes with the growth and multiplication of skin cells. Doctors use methotrexate to treat people whose psoriasis does not respond to other forms of therapy. Liver damage and impaired immunity are possible side effects. Acitretin is particularly effective in treating pustular psoriasis but often raises fat (lipid) levels in the blood and might cause problems with the liver and bones. It can also cause birth defects and should not be taken by a woman who might become pregnant.
Pityriasis Rosea
Pityriasis rosea is a mild disease that causes the formation of many small patches of scaly, rose-colored, inflamed skin.
Pityriasis rosea may be caused by a viral infection.
The most common symptoms are itching, an initial large, tan- or rose-colored circular patch, followed by multiple patches that appear on the torso.
The diagnosis is based on symptoms.
This disease usually resolves with no treatment, and itching that is not severe may be alleviated with artificial or natural sunlight.
The cause of pityriasis rosea is not certain but a viral infection may be involved. However, the disorder is not thought to be contagious. It can develop at any age but is most common among young adults. Pityriasis rosea affects women more often and usually appears during spring and autumn.
Symptoms
Pityriasis rosea causes a rose-red or light-tan patch of skin about 1 to 4 inches (2 to 10 centimeters) in diameter that doctors call a herald or mother patch. This round or oval area usually develops on the torso. Sometimes the patch appears without any previous symptoms, but some people have a vague feeling of illness, loss of appetite, fever, and joint pain a few days before the patch appears. In 7 to 14 days, many similar but smaller patches appear on other parts of the body. These secondary patches are most common on the torso, especially along and radiating from the spine. Most people with pityriasis rosea have some itching, and in some people the itching can be severe.
Phototherapy: Using Ultraviolet Light to Treat Skin Disorders
For many years, people have known that exposure to sunlight is helpful for certain skin disorders. Doctors now know that one component of sunlight—ultraviolet (UV) light—is responsible for this effect. UV light has many different effects on skin cells, including altering the amounts and kinds of chemicals they make and causing the death of certain cells that can be involved in skin diseases. The use of UV light to treat disease is called phototherapy. Psoriasis and atopic dermatitis are the disorders most commonly treated with phototherapy.
Because natural sunlight exposure varies in intensity and is not practical for a large part of the year in certain climates, phototherapy is nearly always performed with artificial UV light. Treatments are given in a doctor’s office or in a specialized treatment center. UV light, which is invisible to the human eye, is classified as A, B, or C, depending on its wavelength. Ultraviolet A (UVA) penetrates deeper into the skin than ultraviolet B (UVB). UVA or UVB is chosen based on the type and severity of the person’s disorder Ultraviolet C is not used in phototherapy. Some lights produce only certain specific wavelengths of UVA or UVB (narrow-band therapy), which are used to treat specific disorders. Narrow-band therapy helps limit the sunburning associated with phototherapy.
Phototherapy is sometimes combined with the use of psoralens. Psoralens are drugs that may be taken by mouth before treatment with UV light. Psoralens sensitize the skin to the effects of UV light, allowing shorter, less intense exposure. The combination of psoralens plus UVA is known as PUVA therapy.
Side effects of phototherapy include pain and reddening similar to sunburn with prolonged exposure to UV light. UV light exposure also increases the long-term risk of skin cancer, although the risk is small for brief courses of treatment. Psoralens often cause nausea. In addition, because psoralens enter the lens of the eye, UV-resistant sunglasses must be worn for at least 12 hours after undergoing PUVA therapy.
Diagnosis and Treatment
A doctor usually makes the diagnosis based on the appearance of the rash, particularly the herald patch. Usually the rash goes away in 4 to 5 weeks without treatment, although sometimes it lasts for 2 months or more. Both artificial and natural sunlight may speed clearing and relieve the itching. Other standard treatments for itching may be used as needed (see page 1283). Corticosteroids taken by mouth are necessary only for very severe itching.
Rosacea
Rosacea (acne rosacea) is a persistent skin disorder that produces redness, tiny pimples, and noticeable blood vessels, usually on the central area of the face.
The cause is unknown.
Typical symptoms include redness, small visible blood vessels, and small pimples that appear on the cheeks and nose.
The diagnosis is based on symptoms and on the person’s age when symptoms first appear.
Worsening of rosacea can be prevented by avoiding certain foods, alcohol, caffeine, and exposure to sunlight, extremes of temperature, wind, and cosmetics.
Treatment includes antibiotics taken by mouth or applied to the skin and antifungal or other medicated creams.
The cause of rosacea is not known. The disorder usually appears during or after middle age—age of onset helps distinguish it from acne. Rosacea is most common among people of Celtic or Northern European descent who have fair complexions but it does affect and is probably under-recognized in darker-skinned people. Although usually easy for doctors to recognize, rosacea sometimes looks like acne and certain other skin disorders. It is often called adult acne.
The skin over the cheeks and nose becomes red, often with small pimples. The skin may appear thin and frail, with small blood vessels visible just below the surface. The skin around the nose may thicken, making it look red and bulbous (rhinophyma).
Treatment
People with rosacea should avoid foods that cause the blood vessels in the skin to dilate—for example, spicy foods, alcohol, coffee, and other caffeinated beverages. Other triggers include sunlight, emotional stress, cold or hot weather, exercise, wind, cosmetics, and hot baths or hot drinks.
Certain antibiotics taken by mouth relieve rosacea. Tetracyclines are usually most effective and produce the fewest side effects. Antibiotics that are applied to the skin, such as metronidazole, clindamycin, and erythromycin, are also effective. In rare cases, antifungal creams, such as ketoconazole or terbinafine cream, are used. Topical azelaic acid gel also can be an effective treatment for rosacea.
Isotretinoin is effective when taken by mouth or when applied to the skin. Corticosteroids applied to the skin tend to make rosacea worse. Severe rhinophyma is unlikely to improve completely with drugs. Therefore, a person with this disorder may need surgery or laser treatment (see box on page 1331).
Lichen Planus
Lichen planus, a recurring itchy disease, starts as a rash of small, discrete red or purple bumps that then combine and become rough, scaly patches.
The cause may be a reaction to certain drugs, chemicals, or infectious organisms.
Typical symptoms include an itchy rash made of red or purple bumps that form into scaly patches appearing on different parts of the body and sometimes in the mouth.
This disease can last for more than 1 year, and it can recur.
Drugs or chemicals that may be causing lichen planus should be avoided.
Lichen planus usually resolves without treatment, but symptoms may be treated with corticosteroids, exposure to ultraviolet light, or lidocaine-containing mouthwashes.
The cause of lichen planus is not known, but it may be a reaction by the immune system to a variety of drugs (especially gold, bismuth, arsenic, quinine, quinidine, and quinacrine), chemicals (especially certain chemicals used to develop color photographs), and infectious organisms. The disorder itself is not infectious.
Symptoms
The rash of lichen planus almost always itches, sometimes severely. The bumps are usually violet and have angular borders. When light is directed at the bumps from the side, the bumps display a distinctive sheen. New bumps may form wherever scratching or a mild skin injury occurs. Sometimes a dark discoloration remains after the rash heals.
Usually, the rash is evenly distributed on both sides of the body—most commonly on the torso, on the inner surfaces of the wrists, on the legs, on the head of the penis, and in the vagina. About half of those who get lichen planus also develop mouth sores. The face is less often affected. On the legs, the rash may become especially large, thick, and scaly. The rash sometimes results in patchy baldness on the scalp.
Lichen planus in the mouth usually results in a bluish white patch that forms in lines. This type of mouth patch often does not hurt, and the person may not know it is there. Sometimes painful sores form in the mouth, which often interfere with eating and drinking.
Prognosis and Treatment
Lichen planus usually clears up by itself after 1 or 2 years, although it sometimes lasts longer, especially when the mouth is involved. Symptoms recur in about 20% of people. Prolonged treatment may be needed during outbreaks of the rash. However, between outbreaks, no treatment is needed. People with mouth sores have a slightly increased risk of oral cancer, but the rash on the skin does not turn cancerous.
Drugs or chemicals that may be causing lichen planus should be avoided, and standard treatments can be used to relieve itching (see page 1283). Corticosteroids may be injected into the bumps, applied to the skin, or taken by mouth, sometimes with other drugs, such as acitretin or cyclosporine. Phototherapy (exposure to ultraviolet light) combined with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light) may also be helpful. This treatment is called PUVA (psoralens plus ultraviolet A). For painful mouth sores, a mouth-wash containing lidocaine, an anesthetic, may be used before meals to form a pain-killing coating.
Keratosis Pilaris
Keratosis pilaris is a common disorder in which dead cells shed from the upper layer of skin plug the openings of hair follicles.
The cause is not known, although heredity probably plays a role. Also, people with atopic dermatitis are more likely to have keratosis pilaris.
The plugs or bumps that occur in keratosis pilaris make the skin feel rough (like chicken skin) and dry. Sometimes the plugs resemble small pimples. Generally, these plugs do not itch or hurt and cause only cosmetic problems. The upper arms, thighs, and buttocks are most commonly affected. The face may break out as well, particularly in children. Plugs are more likely to develop in cold weather and to clear up in the summer.
Treatment is not needed unless the person is bothered by the appearance of the disorder. Skin moisturizers are the main treatment. Creams with salicylic acid, lactic acid, or tretinoin can also be used. Keratosis pilaris is likely to come back when treatment is stopped.