CHAPTER 196

Fungal Skin Infections

Fungi usually make their homes in moist areas of the body where skin surfaces meet: between the toes, in the genital area, and under the breasts. Many fungi that infect the skin (dermatophytes) live only in the topmost layer of the epidermis (stratum corneum) and do not penetrate deeper. Obese people are more likely to get these infections because they have excessive skinfolds. People with diabetes tend to be more susceptible to fungal infections as well.

Strangely, fungal infections on one part of the body can cause rashes on other parts of the body that are not infected. For example, a fungal infection on the foot may cause an itchy, bumpy rash on the fingers. These eruptions (dermatophytids, or id reactions) are allergic reactions to the fungus. They do not result from touching the infected area.

Doctors may suspect a fungal infection when they see a red, irritated, or scaly rash in one of the commonly affected areas. They can usually confirm the diagnosis by scraping off a small amount of skin and having it examined under a microscope or placed in a culture medium where the specific fungus can grow and be identified (see page 1278).

Candidiasis

Candidiasis (yeast infection, moniliasis) is infection by the yeast Candida.

Candidiasis tends to occur in moist areas of the skin.

Candidiasis may cause rashes, scaling, itching, and swelling.

Doctors examine the affected areas and view skin samples under a microscope or in a culture.

Antifungal creams or antifungal drugs given by mouth usually cure candidiasis.

Candida yeast is a normal resident of the mouth, digestive tract, and vagina that usually causes no harm. Under certain conditions, however, Candida can overgrow on mucous membranes and moist areas of the skin. Typical areas affected are the lining of the mouth, the groin, the armpits, the skin under the breasts in women, and the skinfolds of the stomach. Conditions that enable Candida to infect the skin include the following:

Hot, humid weather

Tight, synthetic underclothing

Poor hygiene

Inflammatory diseases (such as psoriasis) that occur in skinfolds

Use of antibiotics or corticosteroids and other drugs that suppress the immune system

Disorders such as diabetes or a weakened immune system

People taking antibiotics may develop candidiasis because the antibiotics kill the bacteria that normally reside on the body, allowing Candida to grow unchecked. Corticosteroids or immunosuppressive therapy after organ transplantation can also lower the body’s defenses against candidiasis. Inhaled corticosteroids, often used by people with asthma, sometimes produce candidiasis of the mouth. Pregnant women, people receiving cancer therapy drugs, obese people, and people with diabetes also are more likely to be infected by Candida.

In some people (usually people with a weakened immune system), Candida invades deeper tissues as well as the blood, causing life-threatening systemic candidiasis (see page 1232).

Symptoms

Symptoms vary, depending on the location of the infection.

Infections in skinfolds (intertriginous infections) or in the navel usually cause a bright red rash, sometimes with softening and breakdown of skin. Small pustules may appear, especially at the edges of the rash, and the rash may itch intensely or burn. A candidal rash around the anus may be raw, white or red, and itchy. Babies may develop a candidal rash in the diaper area (see page 1735).

Vaginal candidiasis (vulvovaginitis, yeast infection—see page 1540) is common, especially in women who are pregnant, have diabetes, or are taking antibiotics. Symptoms of these infections include a white or yellow cheeselike discharge from the vagina and burning, itching, and redness along the walls and external area of the vagina.

Penile candidiasis most often affects men with diabetes, uncircumcised men, or men whose female sex partners have vaginal candidiasis. Sometimes the rash may not cause any symptoms, but usually, the infection produces a red, raw, itching, burning or sometimes painful rash on the head of the penis and sometimes the scrotum.

Thrush is candidiasis inside the mouth (see also page 1232). The creamy white patches typical of thrush cling to the tongue and sides of the mouth and may be painful. The patches cannot be scraped off easily with a finger or blunt object. Thrush in otherwise healthy children is not unusual, but in adults it may signal a weakened immune system, possibly caused by cancer, diabetes, or AIDS. The use of antibiotics that kill off competing bacteria increases the chances of getting thrush.

Perlèche is candidiasis at the corners of the mouth, which causes cracks and tiny fissures. It may stem from chronic lip licking, thumb sucking, ill-fitting dentures, or other conditions that make the corners of the mouth moist enough that yeast can grow.

Candidal paronychia is candidiasis in the nail beds, which causes painful redness and swelling (see page 1339). This disorder typically occurs in people with diabetes or a weakened immune system or in otherwise healthy people whose hands are subjected to frequent wetting or washing.

Diagnosis and Treatment

Usually, doctors can identify candidiasis by observing its distinctive rash or the thick, white, pasty residue it generates. To confirm the diagnosis, doctors may scrape off some of the skin or residue with a scalpel or tongue depressor. The sample is then examined under a microscope or placed in a culture medium (a substance that allows microorganisms to grow) to identify the specific fungus (see page 1278).

Generally, candidiasis of the skin is easily cured with creams containing miconazole, clotrimazole, oxiconazole, ketoconazole, econazole, ciclopirox, or nystatin. The cream is usually applied twice daily for 7 to 10 days. Corticosteroid creams are sometimes used with antifungal creams because they quickly reduce itching and pain (although they do not help cure the infection itself and, used alone, worsen the infection). Candidiasis that does not respond to antifungal creams and liquids may be treated with gentian violet, a purple dye that is painted on the infected area to kill the yeast.

Keeping the skin dry helps clear up the infection and prevents it from returning. Talcum powder helps keep the surface area dry, and talcum powder with nystatin may further help prevent a recurrence.

Different treatments are prescribed for vaginal yeast infections, thrush, and nail infections.

Ringworm

Ringworm (tinea) is a fungal skin infection caused by several different fungi and generally classified by its location on the body.

The fungi that cause ringworm infections tend to spread in moist areas of the skin.

Symptoms include rashes, scaling, and itching.

Doctors usually examine the affected area and view a skin sample under a microscope or in a culture.

Antifungal drugs applied directly to the affected areas or taken by mouth usually cure the infection.

Despite its name, ringworm infection does not involve worms. The name arose because of the ring-shaped skin patches created by the infection. Symptoms vary depending on the location of the infection. Doctors can frequently identify a ringworm infection by its appearance. Most often, there is little or no inflammation and the infected areas are mildly itchy with a scaling, slightly raised border. These patches can come and go intermittently. Areas of the body that are most commonly affected include the head, skin, and nails (infections called tinea unguium and onychomycosis—see page 1339). Treatment varies by site but always involves topical or oral antifungal drugs.

Did You Know…

Ringworm infection is caused by fungi, not by worms.

ATHLETE’S FOOT

Athelete’s foot (tinea pedis) is a fungal infection of the feet.

Tinea pedis is a common fungal infection that usually appears during warm weather. The infection may spread from person to person in communal showers and bathrooms or in other moist areas where infected people walk barefoot. People who wear tight shoes are also at risk. The infection is usually caused by Trichophyton or Epidermophyton. These fungi most commonly grow in the warm, moist areas between the toes. The fungus can produce mild scaling with or without redness and itching. The scaling may involve a small area or the entire sole of the foot. Sometimes scaling is severe, with breakdown and painful cracking (fissuring) of the skin. Fluid-filled blisters can also form. Because the fungus may cause the skin to crack, athlete’s foot can lead to bacterial infection (see page 1315), especially in older people and in people with inadequate blood flow to the feet.

Diagnosis is usually obvious to doctors based on their clinical examination and review of risk factors.

Treatment

The safest treatment is using topical antifungal drugs, but recurrence is common and treatment must often be prolonged. Oral antifungal drugs such as itraconazole and terbinafine are usually most effective but may have side effects. Use of a topical antifungal at the same time may reduce recurrences.

Reducing moisture on the feet and in footwear helps prevent recurrences. Wearing open-toe shoes or shoes that “breathe” and frequently changing socks are important, especially during warm weather. Spaces between toes should be thoroughly towel-dried after bathing. Applying antifungal powders (eg, miconazole), gentian violet, Burow’s solution (5% aluminum subacetate) soaks, or 20 to 25% aluminum chloride hexahydrate powder helps keep the feet dry.

JOCK ITCH

Jock itch (tinea cruris) is a fungal infection of the groin.

Tinea cruris is much more common in men than in women and develops most frequently in warm weather. The infection begins in the skinfolds of the genital area and can spread to the upper inner thighs. Usually the scrotum is not involved (unlike in yeast infection). The rash has a scaly, pink border. Jock itch can be quite itchy and may be painful. A susceptible person may have repeated infections. Flare-ups occur more often during the summer.

The diagnosis is usually obvious to doctors based on a physical examination. Treatment involves anti-fungal cream or lotion. Oral antifungal drugs may be needed in people who have inflammatory or widespread infections or infections that do not heal with use of topical drugs.

SCALP RINGWORM

Scalp ringworm (tinea capitis) is a fungal infection of the scalp.

Tinea capitis is primarily caused by Trichophyton. Scalp ringworm is highly contagious and is common among children (see page 1735). It may produce a pink scaly rash that may be somewhat itchy, or it may produce a patch of hair loss without a rash. Less commonly, it can cause a painful, inflamed, swollen patch on the scalp that sometimes oozes pus (a kerion). A kerion is caused by an allergic reaction to the fungus and may result in scarring hair loss.

Diagnosis

Tinea capitis is diagnosed by physical examination and by the doctor examining a sample of hair or scale from the scalp under a microscope. The sample is prepared with a special solution that helps identify the type of fungus causing the infection.

Treatment

In children, treatment involves an antifungal drug called griseofulvin taken orally for 6 to 8 weeks. An antifungal cream should be applied to the scalp to prevent spread, especially to other children, until the tinea capitis is cured. Selenium sulfide 2.5% shampoo should also be used at least twice a week. Children may attend school during treatment.

In adults, treatment is with the oral antifungal drug terbinafine or itraconazole. How long treatment is needed depends on the drug used. For severely inflamed areas and for a kerion, doctors may prescribe a short course of prednisone to lessen symptoms and perhaps reduce the chance of scarring.

BODY RINGWORM

Body ringworm (tinea corporis) is a fungal infection of the face, trunk, arms, and legs.

Tinea corporis may be caused by Trichophyton, Microsporum, or Epidermophyton. The infection generally produces round patches with pink scaly borders and clear areas in the center. Sometimes the rash is itchy. Body ringworm can develop anywhere on the skin and can spread rapidly to other parts of the body or to other people with whom there is close bodily contact. Diagnosis is usually by physical examination.

Treatment

Tinea corporis is treated with a topical antifungal cream, lotion, or gel applied twice a day and continued for 7 to 10 days after the rash completely disappears. If the cream is discontinued too soon, the infection may not be eradicated, and the rash will return. Several days may pass before antifungal creams reduce symptoms. Corticosteroid creams are often used to help relieve itching for the first few days. Low-dose hydrocortisone is available over the counter. More potent corticosteroids require a prescription and may be used in addition to an antifungal cream. If the ringworm infection oozes, a bacterial infection also may have developed. Such an infection may require treatment with antibiotics, either applied to the skin or taken by mouth.

Topical Antifungal Drugs

Amorolfine

Butenafine

Ciclopirox

Clotrimazole

Econazole

Haloprogin

Ketoconazole

Miconazole

Naftifine

Nystatin (for Candida only)

Oxiconazole

Selenium sulfide (shampoo for tinea versicolor)

Sulconazole

Terbinafine

Terconazole

Tioconazole

Tolnaftate

Undecylenate

Extensive and resistant infections can occur in people infected with Trichophyton rubrum and in people with debilitating systemic (body-wide) diseases. For such people, the most effective therapy is an oral drug, such as itraconazole or terbinafine, taken for 2 to 3 weeks.

BEARD RINGWORM

Beard ringworm (tinea barbae) is a fungal infection of the beard area most often caused by Trichophyton mentagrophytes or Trichophyton verrucosum.

Tinea barbae usually involves superficial circular patches, but deeper infection may occur. An inflammatory kerion may also develop, which can result in scarring hair loss. Tinea barbae is rare. Most skin infections in the beard area are caused by bacteria, not fungi. Doctors diagnose the infection by examining a sample of skin under a microscope.

Treatment is with an antifungal drug, such as griseofulvin, terbinafine, or itraconazole, taken by mouth. If the area is severely inflamed, doctors may add a short course of prednisone to lessen symptoms and perhaps reduce the chance of scarring.

Tinea Versicolor

Tinea versicolor (pityriasis versicolor) is a fungal infection of the topmost layer of the skin causing scaly, discolored patches.

The infection, caused by the yeast Malassezia furfur, is quite common, especially in young adults.

Tinea versicolor rarely causes pain or itching, but it prevents areas of the skin from tanning, producing patches that are lighter in color than surrounding skin. People with naturally dark skin may notice lighter patches. People with naturally fair skin may get darker or lighter patches. The patches are often on the chest or back and may scale slightly. Over time, small areas can join to form large patches.

Diagnosis

Doctors can diagnose tinea versicolor by its appearance. Doctors may use an ultraviolet light to show the infection more clearly or may examine scrapings from the infected area under a microscope to confirm the diagnosis.

Treatment

Topical antifungal cream such as ketoconazole may be used, as well as terbinafine solution spray. Prescription selenium sulfide shampoo is effective if applied full-strength to the affected areas (including the scalp) at bedtime, left on overnight, and washed off in the morning. Treatment is usually continued for 3 or 4 nights. Alternatively, the shampoo can be applied for 10 minutes a day for 10 days. Prescription ketoconazole shampoo is also effective. It is applied and washed off in 5 minutes. It is used as a single application or daily for 3 days.

Antifungal drugs taken by mouth, such as itraconazole, ketoconazole, or fluconazole, are sometimes used to treat widespread, resistant infection (see table on page 1231). However, because these drugs may cause unwanted side effects, topical drugs are usually preferred.

The skin may not regain its normal pigmentation for many months after the infection is gone. Tinea versicolor commonly comes back after successful treatment because the fungus that causes it normally lives on the skin. Therefore, many doctors recommend use of 2.5% selenium sulfide shampoo or ketoconazole shampoo monthly or every other month to prevent recurrences. Pyrithione zinc soap may also be used regularly to prevent recurrence.