Chapter 8
Food Allergies and Asthma
In This Chapter
Categorizing adverse food reactions
Investigating allergic and nonallergic food hypersensitivities
Understanding how food intolerance differs from food hypersensitivity
Getting medical attention for severe food reactions
Preventing allergic food reactions
I f the food you eat bites you back with fits of wheezing, outbreaks of eczema, gastric distress, or other symptoms (perhaps even including life-threatening bouts of anaphylactic shock), you’re not alone. Adverse food reactions affect at least one in four Americans at some point in their lives. Food allergies can even trigger asthma symptoms that, in some cases, cause life-threatening respiratory symptoms in certain susceptible asthmatics.
Types of Adverse Food Reactions
Because the range of adverse food reactions can include a constellation of nasal, respiratory, skin, gastrointestinal, and oral symptoms occurring separately or in combination, doctors usually classify these reactions according to the mechanisms that the reactions involve.
Food hypersensitivity: These reactions occur when your immune system responds to specific proteins in certain foods. The reactions can include allergic mechanisms involving IgE antibodies (see Chapter 1) as well as nonallergic mechanisms.
• Allergic food hypersensitivities include gastrointestinal (GI) tract allergies, hives and other allergic skin reactions, and even anaphylaxis (a severe, abrupt reaction that affects many organs of the body simultaneously and can potentially be life-threatening).
• Nonallergic food hypersensitivities (sometimes referred to as non-IgE food reactions) include syndromes such as food-induced enterocolitis, colitis, and malabsorption, as well as celiac disease, dermatitis herpetiformis, and pulmonary hypersensitivity. I discuss these medical conditions in greater detail in “Nonallergic (Non-IgE) Food Hypersensitivities,” later in this chapter.
Food intolerance: These types of reactions result from nonallergic, nonimmunologic responses to offending substances in various foods. Forms of food intolerance include
• Lactose intolerance
• Pharmacologic food reactions
• Metabolic food reactions
• Food additive reactions
• Food poisoning
• Toxic reactions
Although allergic reactions to food can be severe (and should be appropriately diagnosed and managed), the actual number of adults in the United States who suffer from true food hypersensitivities is closer to 1 percent of the population. However, food allergies may affect as many as 6 percent of infants and children, with allergic reactions to peanuts topping the list of triggers of severe, even life- threatening respiratory symptoms in some children with asthma. According to one recent study of life-threatening asthma attacks, half of the children hospitalized in these cases had food hypersensitivities, especially to peanuts.
Allergic Food Hypersensitivities
Peanuts (the leading cause of severe allergic food reactions), soybeans, peas, lentils, beans and other legumes, and foods containing these products as ingredients. Because a wide variety of foods include peanuts and soybean products as ingredients, these legumes often act as hidden triggers of food allergies. See the section “Anaphylaxis and allergic food reations,” later in this chapter, for more information on peanut issues. Likewise, you can find details on uncovering hidden allergenic ingredients in many common foods in “Avoiding Adverse Food Reactions,” later in this chapter.
Shellfish, such as shrimp, lobster, crab, clams, and oysters.
Fish — both freshwater and saltwater.
Tree nuts, including almonds, Brazil nuts, cashews, hazelnuts, and walnuts.
Eggs, especially egg whites, which contain the predominant allergenic proteins, ovalbumin, and ovomucoid. The yolk is less allergenic than the egg white.
Cow’s milk and products that contain milk protein fractions, such as casein (80 percent of the protein in cow’s milk) and whey, which includes lactalbumin and lactoglobulin.
Wheat, an important ingredient in bran, malt, wheat flour, graham flour, wheat germ, and wheat starch. Corn, rice, barley, oats, and other grains and cereals are less common food allergy triggers.
Of these culprits, the products that trigger allergic food reactions in children most frequently are milk, eggs, peanuts, tree nuts, fish, soy, and wheat. In adults, the likeliest causes of allergic food reactions include fish, shellfish, peanuts, and tree nuts.
Other, less obvious sources of food allergens may possibly cause adverse reactions in a smaller number of susceptible individuals. These much less frequently problematic food allergens (listed in family groupings to keep it all in the family) include the following:
Goosefoot family: Spinach, beets, Swiss chard, pigweed
Gourd family: Watermelon, honeydew, cantaloupe, other melons, pumpkins, squash
Lily family: Onions, leeks, garlic, asparagus
Mustard family: Broccoli, cabbage, cauliflower, horseradish, turnip, radish, mustard
Nightshade family: Tomatoes, potatoes, eggplant, bell pepper, red pepper
Plum family: Apricots, cherries, peaches, almonds, plums
Additives and allergies
Allergic mechanisms may or may not play a part in some adverse food reactions commonly asso- ciated with food additives. When additives are in the picture, identifying a suspected food allergen can get complicated, because finding out whether the food itself or the additive causes the problem is often difficult.
Additives, such as sulfites, are often used as antioxidants to preserve wine, dried fruit, shrimp, and potatoes. These additives have been implicated in cases of allergic food hypersensi- tivities, including potentially life-threatening bronchospasm (constriction of the airways) and asthma symptoms, especially in severe asthmatics who require long-term treatment with oral corticosteroids. (See Chapter 15 for information on long-term asthma therapy and these types of medications.)
Exposure to sulfites, when used in salad bars and in the guacamole served in some restaurants, can trigger asthma symptoms in susceptible asthmatics when they inhale the sulfite fumes from treated foods. These antioxidant additives are sometimes used to prevent discoloration and to keep greens looking perky. That’s why some salad bar lettuce — which may sit out for hours during the day — doesn’t seem to wilt, unlike the salads most of us prepare at home.
The U.S. Food and Drug Administration (FDA) prohibits using sulfites on fresh fruits and vegetables meant to be eaten raw (like with a salad bar) and requires manufacturers to label products that contain sulfites. However, pre- cut or peeled potato products used in some restaurants to make common side dishes (such as french fries and hash browns) may still contain sulfites. Therefore, if you have asthma, always ask questions about the food served in restaurants.
You may need to actually speak with the people preparing your food, such as the chef, or perhaps with a restaurant manager who has precise information on what are the various dishes’ ingredients. Your food server may not have many of those details. If you’re unable to determine whether or not sulfites are being used in certain dishes, you may want to avoid ordering those items altogether.
Doctors often need to be detectives to determine the causes of adverse food reactions. For example, if you experience an adverse food reaction to a hot dog, your doctor must determine whether your reaction is because of allergens in the meat, or whether you’re suffering from hot dog headache due to nitrites used to retard meat spoilage, or even whether you’re reacting to an added food dye that creates the pink coloring.
How allergic food hypersensitivities develop
As I explain in Chapter 1, your inherited tendency to develop allergies can express itself in other allergic conditions also, such as allergic rhinitis (hay fever, see Chapter 7) and atopic dermatitis (eczema). The predisposition toward allergies passes between generations, but the specific allergies themselves may not. Therefore, Mom may be allergic to lobster, Junior may break out in hives after eating peanuts, and baby Betty may get congested after drinking cow’s milk formula.
The severity of your symptoms may also depend on your sensitivity level to particular food allergens and the quantities of these foods you consume. In some cases, ingesting small amounts of these foods may not trigger adverse reactions.
Gastrointestinal tract allergies
Gastrointestinal food hypersensitivity reaction: This reaction generally occurs with other atopic conditions, such as allergic rhinitis and atopic dermatitis, and can cause nausea, stomach pain, vomiting, and, in some cases, diarrhea. In rare cases, a widespread systemic reaction such as anaphylaxis can also result. (See “Anaphylaxis and allergic food reactions,” later in this chapter.)
Cow’s milk allergy: More than 2 percent of infants develop allergies to the proteins casein and whey (including lactalbumin and lactoglobulin) in cow’s milk, resulting in adverse reactions (such as colic, vomiting, and diarrhea) even to minute amounts of these proteins. This reaction isn’t the same as the more familiar syndrome known as lactose intolerance, which is a nonallergic, nonimmunologic response rather than an IgE-mediated reaction.
Allergic eosinophilic gastroenteropathy: This rare condition can cause nausea and vomiting following meals, abdominal pain, and diarrhea. If not managed effectively, this type of allergy can result in malabsorption (poor absorption of food nutrients) and malnutrition, leading potentially to stunted or slowed growth in infants and weight loss in adults.
Oral allergy syndrome: If you have allergic rhinitis, you may also experience oral allergy symptoms after consuming certain fresh fruits and raw vegetables. This cross-reactivity syndrome can occur if you’re sensitive to ragweed pollen (with bananas and melons such as cantaloupe, honey-dew, and watermelon), birch pollen (with apples, carrots, potatoes, hazelnuts, and members of the plum family), and mugwort pollen (with celery, apples, and kiwi fruit). Your symptoms may include severe itching and swelling of the lips, tongue, and palate, as well as blistering of the throat and the mouth’s mucus lining.
Because these fruits and vegetables seem to trigger reactions only in their raw state, you may be able to consume these foods in cooked or frozen forms. However, make sure that you check with your doctor before you cook up that vegetable stir-fry or cool off with a melon sorbet.
Hives and other food-related skin reactions
Allergic food hypersensitivities involving IgE antibodies can also trigger skin reactions in people whose atopic predisposition shows up through skin conditions. These conditions include
Atopic dermatitis (eczema): Eggs, milk, peanuts, tree nuts, soybean, and wheat can contribute to outbreaks in more than one-third of children affected by this skin condition.
Urticaria (hives): These itchy welts can erupt from various types of reactions to many foods including peanuts, tree nuts, milk, eggs, fish, shellfish, soybeans, and fruits, as well as food additives such as sodium benzoates, sulfites, and food dyes. Skin contact with raw meats, fish, vegetables, and fruit can also trigger hives. Allergic-food hypersensitivities are more likely to act as triggers of rapid-onset urticaria (a particularly quick and severe eruption of hives) in children than in adults. Food-related exercise-induced anaphylaxis, which I discuss later in this chapter, can also trigger hives and angioedema.
Angioedema:
Also known as deep swellings, this condition results in deeper tissue inflammation and skin swelling, and is more likely to produce painful and burning sensations rather than itching. Angioedema can erupt as a reaction to the same food allergens that trigger hives.
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Anaphylaxis and allergic food reactions
The most extreme of all allergic food symptoms is anaphylaxis. This abrupt, systemic allergic reaction, often caused by the same foods that trigger hives and angioedema, affects several organs simultaneously and can quickly turn life-threatening. In recent years, the incidence of this severe, and sometimes fatal, reaction has been rising at an alarming rate among asthmatics, with most of these episodes due to accidental ingestion of peanuts, tree nuts, or seafood.
What is particularly disturbing is the fact that so many of these known high-risk patients are aware of their diagnosis but still don’t carry appropriate emergency medication, such as an epinephrine kit, when they experience their anaphylactic reaction, or don’t receive immediate, potentially life-saving emergency care in time.
Generalized urticaria (Total body hives)
Common triggers of total body hives include foods such as peanuts and shellfish (in people who have extreme hypersensitivities to these foods), severe allergic reactions to medications such as penicillin and related compounds, generalized hypersensitivity to latex, and/or extreme sensitivities to insect stings, including those of honeybees, yellow jackets, wasps, hornets, and fire ants.
Food-dependent exercise-induced anaphylaxis
Food-dependent exercise-induced anaphylaxis, a variant of exercise-induced anaphylaxis — which I explain in Chapter 9 — can occur when you exercise within three to four hours after eating a particular food. Two forms of this condition exist.
You may develop anaphylaxis if you ingest particular foods, especially celery, shellfish, wheat, fruit, milk, or fish, prior to exercise. If you experience this reaction and you can identify the specific foods that trigger your episodes, your doctor may advise allergy skin testing (see Chap- ter 11) to confirm your sensitivity to the suspected foods.
You may develop anaphylaxis while exercising, regardless of the type of food you’ve consumed.
Avoiding peanut problems in children
Keep these important points in mind about peanuts and children:
Many foods contain peanuts as a not-so-obvious added ingredient. Therefore, examine all food labels for peanut ingredients and carefully select menu items when dining out with a child who is allergic to peanuts. (See “Avoiding Adverse Food Reactions,” later in this chapter, for more information on foods that contain peanuts.) You may want to pack your child’s lunch to reduce the risk of your child unknowingly consuming foods with minute traces of peanuts in school lunches.
Because so many foods include peanuts as ingredients, instruct your young child not only to avoid peanuts but also never to accept foods — particularly snacks and candy bars — from others, especially playmates and young siblings.
Because the peanut food allergy issue has received widespread media attention, some airlines are introducing peanut-free flights. If you suffer from food allergies of any kind, however, ask questions about the food on your flight, even if the airline claims that no peanuts or peanut ingredients are in the snacks or meals.
A child who has a peanut hypersensitivity should wear a MedicAlert bracelet, especially at school. Also, ask your family doctor about supplying your child’s school with an emergency epinephrine kit. Make sure school personnel know how and when to administer this medication.
Preparing for emergency treatment for anaphylaxis
Medications your doctor has prescribed for you in the event of an anaphylactic reaction
A list of your symptoms
A written treatment plan prepared by your physician
Your physician’s name and contact information
If you’re treated for anaphylaxis, don’t be surprised if you continue to be observed in the emergency room for several hours after responding to initial rescue therapy. Unfortunately, in a few cases, patients who have responded well to initial anaphylaxis treatment have been immediately discharged from the emergency room but within a few hours have experienced a severe late-phase, or second reaction, known as biphasic anaphylaxis.
Managing and preventing anaphylaxis
Food hypersensitivity is a leading cause of anaphylaxis. Current estimates are that as many as 125 people in the United States die each year from food-induced anaphylactic reactions. As you may expect, the most effective long-term method for preventing food-induced anaphylactic reactions is to avoid eating foods that trigger the reaction. I provide more details on avoiding food allergens and establishing a safe diet in “Avoiding Adverse Food Reactions,” later in this chapter.
Nonallergic (Non-IgE) Food Hypersensitivities
Food-induced enterocolitis syndrome: This condition primarily occurs in infants between 1 and 3 months of age. Characteristic symptoms include prolonged vomiting and diarrhea, often resulting in dehydration. Triggers are usually the proteins in formulas that contain cow’s milk or soy substitutes. Occasionally, breastfed infants may also suffer from this syndrome, presumably as the result of a protein ingested by the mother and transferred to the infant in maternal milk. Similar symptoms can occur in older children and adults in response to eggs, rice, wheat, and peanuts. However, most children outgrow this type of hypersensitivity by their third birthday.
Food-induced colitis: Cow’s milk and soy protein hypersensitivity have been implicated in this disorder, which can occur in the first few months of life and is usually diagnosed through the presence of blood in the stools, either seen by the naked eye or hidden (occult), of children who otherwise appear healthy. This condition often diminishes after 6 months to 2 years if children avoid the implicated food allergens.
Feeding a hypoallergenic formula to your baby may help overcome food-induced colitis.
Malabsorption syndrome:
This condition involves hypersensitivities to proteins in foods such as cow’s milk, soy, wheat and other cereal grains, and eggs. Symptoms include diarrhea, vomiting, and weight loss or failure to gain weight.
Celiac disease:
This condition is a more serious form of malabsorption syndrome, and it can cause intestinal inflammation. Symptoms range from diarrhea and abdominal cramping to anemia and osteoporosis. Celiac disease only seems to occur in people who inherit an atopic predisposition. Affected individuals develop a hypersensitivity to a component of gluten called gliadin, which you find in wheat, oats, rye, and barley. If you suffer from this syndrome, however, you’re not necessarily doomed to a life without pasta and pancakes. Resourceful sufferers of celiac disease have come up with many gluten-free products, ranging from beer to pretzels.
Dermatitis herpetiformis:
This condition is a non-IgE-mediated food hypersensitivity to gluten that produces skin eruptions in addition to causing intestinal inflammation. Typical symptoms include a chronic, itchy rash that appears primarily on the elbows, knees, and buttocks, although the disease can affect other areas as well.
Pulmonary hypersensitivity:
This rare condition, induced by cow’s milk, primarily affects young children. Characteristic symptoms include a chronic cough, wheezing, and severe anemia. Removing the offending dairy products from the diet can substantially alleviate symptoms.
Understanding the Differences between Food Allergy and Food Intolerance
As I explain earlier in this chapter, many adverse food reactions don’t involve an immune system response. These types of direct, nonimmunologic reactions are considered signs and symptoms of food intolerance and include the conditions that I explain in the following sections.
Lactose intolerance
If you’re lactose intolerant, odds are your body doesn’t produce sufficient amounts of the lactase enzyme in order for you to properly digest cow’s milk. If you drink milk or consume foods with high milk content, you may experience stomach cramps, bloating, nausea, gas, and diarrhea.
Metabolic food reactions
In some cases, eating average or normal amounts of particular foods (especially fatty foods) may disrupt your digestive system. These disruptions, called metabolic food reactions, may be caused by
Medications (for example, antibiotics) you’re taking for illnesses
A disease or condition (such as a gastrointestinal virus) that may affect your digestive system
Malnutrition (for example, due to vitamin or enzyme deficiency)
Pharmacologic food reactions
Grapefruit juice, which is usually harmless, sometimes causes harm- ful interactions when taken with calcium channel blockers, such as Procardia.
If you have a heart condition, ask your doctor about possible interactions between grapefruit juice and any over-the-counter (OTC) or prescription antihistamines you may take.
If you take blood-thinning drugs such as Coumadin, check with your doctor before eating foods rich in vitamin K like broccoli, spinach, and turnip greens, because they can reduce the medications’ effectiveness.
A harmful potassium buildup can occur if you overindulge on bananas while taking ACE inhibitors, such as Capoten and Vasotec.
Avoid foods high in tyramine, such as cheese and sausage, if you take MAO inhibitors, because the combination can cause a potentially fatal rise in blood pressure. Tyramine may also aggravate or trigger migraine headaches.
The caffeine in coffee, tea, and colas can interact badly with ulcer medications such as Tagamet, Zantac, and Pepcid AC. If your doctor prescribes theophylline for your asthma, reduce your caffeine intake, because caffeine can worsen side effects, such as GI irritation, headache, jitteriness, and sleeplessness.
Food additive reactions
Doctors associate many types of food additives with adverse food reactions. The most frequently implicated food additives are
Monosodium glutamate (MSG): When consumed in large quantities, this flavor enhancer reportedly causes burning sensations, facial pressure, chest pain, headache, and, in rare cases, severe asthma symptoms. Although many sufferers associate these types of reactions with eating Chinese or other types of Asian foods, no conclusive studies have determined a clear link between consuming MSG and adverse food reactions. In any event, with the recent increase of MSG-free restaurants in many parts of the United States, you should have no trouble finding a place to chow down on chow mein without suffering ill effects.
Tartrazine (yellow dye No. 5): This and other food dyes can aggravate chronic hives and may actually be an ingredient in the very same children’s syrups used to treat allergic symptoms such as hives — another good reason to always check medication labels.
Sulfites: Commonly found in processed foods and almost always in wines, sulfites can produce respiratory difficulties. In some cases, sulfites can also trigger potentially life-threatening airway constriction and asthma symptoms in some individuals (see the sidebar “Additives and allergies,” earlier in this chapter).
Food poisoning
Researchers believe that many cases of illness mistakenly diagnosed as the 24-hour flu bug are actually the result of ingesting tainted foods. A particular reaction from spoiled fish, known as scombroidosis, can mimic food allergy due to the release of histamine-like chemicals. Itching, hives, and even shortness of breath can occur depending on the amount of spoiled fish a person has eaten.
Diagnosing Adverse Food Reactions
In order to diagnose your adverse food reactions, your physician should take a detailed medical history and conduct a physical examination. Your doctor may also ask you about the specific details of your reaction to figure out what may cause your reactions.
Keeping a food diary
A well-kept food diary can assist you in telling your doctor about the following items:
The timing of your reactions. For example, do they occur immediately after you’ve consumed a food or liquid, and if not, how long afterward?
The amount of food that seems to trigger a reaction.
Where and how the food was prepared.
The duration and severity of your symptoms.
Any activities, especially exercise, associated with your reactions.
Considering atopic causes
As part of the physical examination, your doctor should also look for signs of atopic diseases, including
Dry, scaly skin, which can indicate eczema
Dark circles under your eyes, which may indicate hay fever
Wheezing and coughing, which can signal asthma symptoms
Eliminating possible food culprits
In some cases, your doctor may advise an elimination diet for you as a way of confirming what triggers your adverse reactions. This process involves eliminating suspected foods from your diet, one at a time, under your doctor’s supervision. If your symptoms significantly improve, your doctor may then gradually reintroduce the likeliest food suspect to determine whether it’s the source of your woes.
Testing for food allergens
If your doctor can’t readily identify the cause of your reactions, he or she may also recommend confirming a suspected food allergen with the allergy tests that I describe in the following sections.
Skin testing
Skin testing involves using specific food extracts to evaluate your sensitivity to suspected allergens. Only a qualified specialist, such as an allergist, should perform skin testing. Skin testing for food allergens isn’t always recommended.
In general, prick-puncture tests are the only skin tests that your doctor needs to administer when attempting to identify suspected food allergens. (See Chap- ter 11 for more about prick-puncture tests.)
Oral food challenges
Oral food challenges involve actually ingesting — under medical supervision — minute quantities of food that contain suspected allergens.
To ensure the most accurate diagnosis, your doctor should administer an oral food challenge while you’re symptom-free, usually as a result of a food elimination diet. Depending on the severity of your adverse food reactions and the type of food allergen that your physician suspects as the cause, your doctor may choose to administer one or more of the following types of oral food challenges:
Open challenge: In this type of test, your doctor informs you of what type of food you’re ingesting.
Single-blind challenge: With this test, your doctor doesn’t inform you of what you’re eating. However, your doctor or the clinician administering the test knows the ingredients.
Double-blind, placebo-controlled oral food challenge (DBPCOFC): This elaborate procedure is the gold standard for identifying food allergens. Neither you nor your doctor (nor the clinician who administers the test) knows the contents of the test. A third party, such as a nurse or a lab technician, prepares the opaque capsule for testing. In most cases, your doctor schedules a DBPCOFC so you can fast for a prescribed amount of time beforehand. You also need to stop taking antihistamines (based on your doctor’s advice) prior to the challenge, because these drugs can interfere with the accuracy. The initial dose of the suspected food in this test is usually half of the minimum quantity that your doctor estimates as the trigger for your reaction. After the test, the technician identifies the capsule’s contents to help your doctor make the proper diagnosis.
Take this challenge only in a facility equipped to treat potentially severe reactions. If your history of adverse food reactions is life-threatening, your doctor will most likely advise you that an oral food challenge is too risky.
Radioallergensorbent testing (RAST)
Your doctor may recommend radioallergensorbent testing, a type of blood test that measures levels of food-specific IgE antibodies in your blood, if skin testing or oral food challenges seem too risky. Most allergists rarely use RAST because it isn’t as accurate as skin testing and may result in an incomplete profile of your allergies. For more information on this test, see Chapter 11.
Avoiding Adverse Food Reactions
For updates and information on food allergens and related issues and to find out how to decipher ingredients listed on food labels, contact The Food Allergy & Anaphylaxis Network at 800-929-4040 or visit the organization’s Web site at www.foodallergy.org .
Make sure that your family, friends, and colleagues all understand what causes your adverse food reactions. You can then minimize the chances of erupting in hives at the Thanksgiving meal or during that crucial dinner with your boss and the company’s new clients.