to the editor: The article,1 “Environmental Control of Allergic Diseases,” in American Family Physician presents an excellent organized schema for environmental control of common inhalants that contribute to asthma and allergic disease. However, the authors do not mention ingestants that also can trigger reactivity of the respiratory tract. For example, foods induce respiratory symptoms by both reaginic and nonreaginic mechanisms; moreover, food allergies commonly coexist with inhalant allergies. One study2 showed that 43 percent of asthmatic patients who were placed on a diet that eliminated common allergens substantially improved compared with only 6 percent of subjects in the control group.
A proper diagnosis of specific food allergies often requires screening tests for evidence of food-specific IgE allergy and proof of reactivity through elimination diets and oral food challenges.3 Double-blind, placebo-controlled food elimination and rechallenge is considered the “gold standard” for diagnosis of food allergies4 in contrast to skin prick tests and radioallergosorbent tests, which are sensitive indicators of food-specific IgE antibodies but poor predictors of clinical reactivity.5 In many situations, the diagnosis of food allergy may rest simply on a history of an acute onset of typical symptoms, such as wheezing following the isolated ingestion of a suspected food.6
in reply: Dr. Anderson correctly points out that we did not mention in our article1 that ingestants can trigger reactivity of the respiratory tract. However, the bulk of the literature on this subject indicates that the frequency of significant asthma exacerbation caused by food allergy is low,2,3 and the vast majority of reactions are caused by a small number of foods such as peanuts, fish, shellfish, eggs, and cow's milk.4 Persons tend to outgrow allergies to milk and eggs but not to nuts and fish; peanuts are the most common food allergen in children more than three years of age.4 National and international asthma guidelines recognize that food allergy is an uncommon cause of asthma exacerbation.3,5 Atopic dermatitis is much more likely than asthma to be caused by food allergy. One study6 showed that one third of children with refractory atopic dermatitis had clinical reactivity to food proteins.