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| Food Allergies Adverse reactions to foods can occur for many reasons, only some of which are based on allergy. Allergy, by definition, means that an immunological reaction can be demonstrated as the basis of the adverse reactions (see WHAT ARE ALLERGIES?). In many patients, significant clinical improvement can be produced by eliminating certain foods or food additives from the diet. In only some of these people can an immunological reaction be demonstrated by allergy testing (see ALLERGY TESTING). It is for this reason that food "allergy" continues as one of the poorest understood areas of allergy, and one of the most debated among allergists.
Adverse food reactions can be divided into classic IgE mediated food allergy, oral allergy syndrome, apparent food "allergy", and food intolerance.
CLASSIC IgE MEDIATED FOOD ALLERGY · frequency greatest in infancy and early childhood, and declines over the first decade of life · six foods account for 90% of food allergy in children: milk, egg, peanut, wheat, soy and tree nuts · four foods account for 90% of food allergy in adults: peanut, tree nuts, fish and shell fish · some infants "outgrow" their allergies to egg, milk and soy · some food allergies rarely outgrown: peanut, tree nuts, fish, shellfish · symptoms typically begin within minutes of eating the food · can cause allergic rhinitis, asthma, atopic dermatitis (eczema), urticaria/angioedema, and most significantly, life-threatening anaphylaxis · symptoms may be limited to local reactions in the mouth, throat, or gastrointestinal tract, or may involve other organs of the body including skin, upper and lower respiratory tract, eyes, and cardiovascular system · by definition, caused by immunological reaction with positive allergy test
ORAL ALLERGY SYNDROME · local symptoms of itching in mouth and throat after eating certain fruits and vegetables · frequently occurs in people with seasonal allergic rhinitis (hay fever) with symptoms often worse during the patient’s inhalant allergy season · appears to be due to cross reactivity between inhalant allergens and certain foods:
· symptoms begin within minutes of eating the food and resolve quickly
APPARENT FOOD "ALLERGY" · frequency most common in infancy and early childhood, but not uncommonly found in adults with classic allergic diseases and negative allergy testing results · most common foods: milk, egg, wheat, corn, yeast, soy, tomato, potato and citrus fruits · symptoms commonly do not become obvious for 1 to 8 hours after eating the food · patient’s medical history often begins in infancy with feeding problems (spitting up, vomiting, diarrhea, colic) and progresses to include any of the following clinical conditions:
· often the way these apparent food allergies show up can change with ages (e.g., eczema as infant, recurrent ear infections as toddler, asthma as older child, and irritable bowel syndrome as adult) · allergy tests are negative · diagnosis made by well-controlled elimination diets under physician supervision · occasionally found to be the "cause" of patients with classical allergic diseases and negative allergy tests (e.g., vasomotor rhinitis, intrinsic asthma) · occasionally found to be the cause of poor patient response to treatment of inhalant allergy through avoidance and/or allergy immunotherapy (see MANAGEMENT OF ALLERGIC DISORDERS)
FOOD INTOLERANCE · cause of many adverse reactions to foods · not caused by immunological reaction · frequently caused by:
TREATMENT · avoidance of the identified food is only proven method of prevention · drugs are used to treat the symptoms produced (see specific allergic disorders)
· education for all who deal with food allergic patients of the existence of food allergy and the need for emergency treatment to prevent potentially tragic fatalities · some recommended "treatments" for food allergy are experimental in nature without substantial scientific validation (e.g., "sublingual drop therapy", anti-fungal treatment for "yeast" allergy)
TIPS · "apparent" food allergies frequently pass in families from generation to generation, often with differing clinical presentations · elimination diets are most successful when performed out of a person’s inhalant allergy season (not during the pollen season) after avoidance measures have been completed in the home and work environments for indoor allergens and when the person is free of infection · elimination diets are not easy, and are most successful when performed under the direction of a trained allergist who understands the treatment of food allergy. |
