Food allergies and reactions
By Clifford W. Bassett, MD, FAAAAI
Food allergies can be a pervasive, potentially life-threatening problem affecting six to seven million Americans. About 8 percent of the children in the United States (2 million children) are estimated to be affected by allergic sensitivities to foods.
Among infants and toddlers, 6% to 8% may experience food allergic reactions, a higher prevalence than physicians previously thought. The presence of food allergies seems to be higher in the first several years of life. A child with allergies, such as eczema and/or seasonal allergies is more likely to have food allergic sensitivities.
The actual incidence of food allergies is much less common among adults (2.5%), especially when compared to surveys that estimate at least 20% of adults believe they have a food allergy.
Physiology of a food allergy reaction
In a food-allergic reaction, an individual’s immune system overreacts to specific food proteins that ordinarily do not create a problem. During the allergic reaction, chemicals including “histamines,” are released that trigger allergic symptoms that can than affect the eyes, nose and throat, as well as the skin and the lungs.
Many food allergens may still cause an allergic reaction even after they are cooked. Even a trace amount of a food can cause a reaction in some very sensitive individuals.
There is a broad range of allergy symptoms experienced by both adults and children with food allergies, which can develop within minutes up to several hours after ingestion, that include itchiness of the mouth, facial and tongue swelling, hives, difficulty breathing, abdominal pain and vomiting and in extreme cases, a drop in blood pressure [anaphylactic shock].
In the United States, the most likely common allergens in adults and children are: cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and nuts.
Peanut and food anaphylaxis
While peanut allergy prevalence has increased in recent decades, the causes are unknown. Possible explanations have included a history of allergies, a family history of peanut allergy, prenatal exposure to peanuts, and exposure to peanut oils (e.g., from diaper creams) upon contact with infant skin.
Peanut allergy is generally recognized as the number one cause of severe or fatal allergic reactions in children and adults in the United States. A life-threatening and sudden event occurs after ingestion of food that initiates the allergic cascade, better known as anaphylaxis.
Peanut allergy is believed to be the leading cause of severe or life-threatening food-induced allergic reactions, causing an estimated 15,000 emergency room visits each year and nearly 100 deaths. Certain food allergies may be more likely to have long-lasting or lifelong effects, including peanuts, tree nuts and/or shellfish. Recent data indicates that up to one-fifth of persons allergic to these foods may actually lose their allergic sensitivities over time.
Diagnosis of a food allergy
An allergist/immunologist will determine whether a food allergy exists after taking a thorough history, examination and utilization of food allergy tests. When allergy skin testing is performed, and if a probable allergy to a specific food exists, a small wheal [a raised bump] will develop at the test site. Your doctor may also order a blood test [RAST or CAP RAST] to evaluate if food allergies are present. If the diagnosis is still not certain, a supervised food challenge may be needed to settle whether you actually have a true food allergy.
Prevention and treatment of an allergic reaction
The most important steps for treating a reaction are to understand and recognize early symptoms, react immediately and follow your doctor’s instructions for treatment. You also need to be prepared for emergencies that may occur both at home and away from home, including understanding the need for and correct usage of injectable epinephrine (i.e. an EPI-Pen auto-injector), as well as having antihistamines on hand. Epinephrine helps to reverse an anaphylactic reaction once in progress.
However, in spite of your best efforts at avoidance, reactions may occur. The best possible treatment is successful prevention and education for food allergy sufferers, as well as school and work personnel, coaches and family members.
Many patients who self-diagnose a food allergy never seek medical attention from an allergist/immunologist. This intervention improves allergen avoidance strategies and provides food allergic individuals with proper treatment tools for severe reactions.
Food labels
A recent FDA study found that up to one quarter of products sampled contained undeclared ingredients, including common foods such as nuts and egg products. Only about one half of food processing companies could verify that the ingredients were accurate and complete.
Avoidance of the suspect foods and related ingredients by reading food labels is important for food-allergic people. Become familiar with technical names of ingredients. Cow’s milk proteins can be listed by alternative names such as milk solids, whey and caseinate, and egg is sometimes listed as albumin. Always ask a server in the restaurant about possible hidden ingredients or food contaminants if you have food sensitivities.
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Cross reactivity and oral allergy syndrome
With some foods, an allergy to one food may render sensitivity to other foods in the same food classification. For some people, seasonal allergy symptoms may be made worse by consuming fresh fruits due to “oral allergy syndrome.”
Ingestion of “cross-reactive” proteins present in some foods including peach, apple, pear, cherry, carrot, hazelnut, cherries, carrots, kiwi, hazelnut, almonds among others, will cause itchiness of the mouth and throat in people with allergies to birch tree pollens. Ingestion of other foods/supplements such as banana, cucumber, melon, zucchini, sunflower seeds, chamomile tea and even Echinacea will cause a similar reaction in individuals with ragweed allergies.
Food-dependent exercise-associated reactions
Food-dependent exercise-induced reactions are uncommon, but have been described in females more, especially those with allergies and/or asthma. This reaction is seen only when an individual eats a specific food [e.g., wheat, shellfish, fruit, milk, celery, and fish have been reported] and exercises within hours after eating.
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What’s new in food allergy research?
- The American Academy of Pediatrics’ has recent recommendations for preventing or delaying the onset of food allergies in infants/children from allergic families. A brochure is now available through the Food Allergy and Anaphylaxis Network for expectant and nursing mothers.
- In a study of Norwegian children with allergic mothers who had C-section deliveries, the rate of perceived and objectively confirmed allergies to a variety of foods was seven-fold higher than non-c-section deliveries. This indicated that in predisposed children an increase in the risk for food allergy may be observed in children who were born by c-section.
- Clinical studies of an anti-IgE drug for peanut allergy have yielded positive results, including increasing an individuals threshold upon which an allergic reaction will occur, in clinical trials in individuals with peanut allergies
- Peanut allergies in children may occur from low dose exposure of peanut protein upon skin contact with peanut oil products, according to a report in the New England Journal of Medicine.
- For further information, go online to the American Academy of Allergy, Asthma and Immunology at www.aaaai.org. Their patient information line is 800-822-2762. The Food Allergy and Anaphylaxis Network can be reached at 800-929-4040, and their Web site is www.foodallergy.org.
