The prevalence of food allergies has increased significantly in the last 20 years, now affecting an estimated 6 to 8 percent of children and 2 percent of adults. The incidence of food-induced anaphylaxis (life-threatening allergic reactions) is approximately 30,000 cases per year, resulting in nearly 150 deaths. The majority of adverse food reactions are not caused by allergies. Problems are generally divided into immune or nonimmune responses. An example of a nonimmune reaction is lactose intolerance, which is caused by a deficiency of the enzyme lactase. People with this condition develop gas, bloating and diarrhea after drinking milk. Toxic reactions, such as scombroid fish poisoning which causes flushing, are also nonimmune reactions.
Immune responses are divided into immunoglobulin E (IgE) and non-IgE reactions. Celiac disease is an example of the latter and it is caused by an immune response to gluten, a protein found in wheat and other grains. Symptoms can include abdominal pain, diarrhea, bloating, anemia and weight loss. Food allergies triggered by IgE are potentially the most serious. These antibodies attach to cells called
EXERCISE ALLERGY?
A little known subset of food-induced anaphylaxis is food-dependent exercise-induced anaphylaxis. It occurs when exercising within two to four hours after eating. Symptoms include itching, flushing, hives, chest tightness, hypotension and shock. There are two forms: one occurs when exercising after eating a specific food to which one is allergic and the other occurs when exercising after eating any food. Other contributing factors include heat and ingestion of aspirin-like medications and alcohol.
basophils found in the blood, and mast cells in skin, upper respiratory tract, lungs and gastrointestinal tract. These cells release histamine and other inflammatory agents when an allergic reaction is triggered. The reaction can be mild to life-threatening. A life-threatening reaction is called anaphylaxis.
IgE events usually develop within 15 to 60 minutes of eating a food. The symptoms depend on the tissue involved and the severity of the allergy, including:
Oral: itching, tingling or swelling of the lips or tongue
Throat: tightening, swelling, hoarseness
Lung: shortness of breath, coughing, wheezing, tightness
Gut: nausea, vomiting, cramps, diarrhea
Skin: hives, swelling of face or extremities, eczema
Cardiovascular: weak and shallow pulse, pale, passing out
A new medication, called omalizumab, removes 95 percent of IgE antibodies. It is presently approved for treatment of severe
allergic asthma. Preliminary studies suggest it can also be very effective in preventing food reactions. If further studies confirm these results, it should be available in the next year or two for treatment of severe food allergies. Any food can cause an allergic reaction. Eggs, milk, wheat, soy, peanuts, tree nuts, fish and shellfish are the most common. Children usually outgrow allergies to eggs, milk, soy and wheat by age 5. Allergies to peanut, tree nuts and seafood are usually not outgrown by children or adults. There is no proven way of preventing food allergies in infants and children. Present recommendations for high-risk infants include breast-feeding for six months and avoidance of peanuts and tree nuts (and possibly eggs, milk and seafood) by nursing mothers. The introduction of solid foods should be delayed until 6 months of age, and major allergens, such as peanuts, nuts and seafood, should be introduced after age 3.
A recent review of 32 fatal food reactions found the age range of those who died was between 2 to 33 years. Most of them had asthma and 94 percent had a prior reaction to the food. The majority of food reactions was caused by peanuts and nuts. Only 10 percent of the individuals had epinephrine with them at the time of the reaction. People with potentially serious food allergies should carry self-injectable epinephrine and a fast-
acting antihistamine with them at all times. An emergency plan should be discussed with your physician. Epinephrine is
available by prescription (EpiPen and Twinject). Benadryl is available over-the-counter and now includes dissolvable tablets. Children should have access to these medications at home, school, day care, and so on. Medical alert bracelets should also be worn. The most effective treatment of a food allergy is avoiding the offending allergen. This can be difficult because many items can be “hidden” in other foods. Fortunately, a federal law became effective on Jan. 1, 2006, requiring food manufacturers to clearly state in English the presence of major food allergens in their ingredients. These foods include milk, eggs, fish, shellfish, tree nuts, peanuts, wheat and soybeans. This should help prevent the accidental ingestion of these foods.
Another common food allergy, called oral allergy syndrome, occurs in people allergic to pollen. When they eat fruits and vegetables that cross-react with pollen, they can develop itching and swelling in their mouth and throat. The reactions are usually mild. These foods include tree fruits such as apples, peaches and cherries; hazelnuts; and carrots and celery which cross-react with birch pollen. Melons and bananas cross-react with ragweed pollen; and tomatoes, watermelon, potato and kiwi can cross-react with grass pollen. For more information on food allergies, visit www.overlake
hospital.org or The Food Allergy
and Asthma Network at www.foodallergy.org.
