Food Allergies

Definition, Prevalence and Diagnosis

Allergies are defined as a condition where protein content of foods (antigen) triggers an immune system reaction in persons allergic to these foods. Presence of immunological characteristics (i.e., immunoglobulin E, antibody production, and release of cellular chemicals that cause allergy symptoms) help distinguish food allergies from other types of food sensitivities. Food sensitivities are intolerances (e.g., lactose intolerance), metabolic disorders (e.g., Phenylketonuria), and idiosyncratic reactions like those to food additives and preservatives (e.g., sulfite-induced asthma). To illustrate the difference, a lactose intolerant person may experience non-life-threatening symptoms such as bloating and diarrhea when milk is ingested. However, a drop of milk can be fatal for somebody with a true food allergy to milk.

Allergies are the sixth leading cause of chronic disease in the United States, costing the health care system $18 billion annually. Virtually any food can cause an allergic reaction. Over 160 foods that can cause allergic reactions have been identified but the following 8 are the most common: peanuts, tree nuts, milk, eggs, soy, fish, shellfish, and wheat. Peanut, tree nut, fish, and shellfish allergies are rarely outgrown. Peanut or tree nut allergies affect approximately 3 million Americans and cause the most severe food-induced allergic reaction. It is impossible to assure a parent that the child-care center will be free of peanuts or peanut residue.

Upon exposure to an offending food, onset and severity of symptoms varies from person to person. Clinical symptoms may occur alone or in combination and include sneezing, runny nose, shortness of breath, skin rashes, hives, eczema, diarrhea, and vomiting. In the worst case scenario individuals may experience anaphylaxis, a life-threatening reaction that begins within minutes; emergency treatment with epinephrine is usually administered to prevent death.

True food allergies affect less than 2% of the population and are most prevalent in infants and young children (4–8%). However, prospective studies have demonstrated that approximately 85% of confirmed symptoms are absent by 3 years of age. The ability to develop a food allergy is inherited and risk increases in presence of family history and/or other types of allergies (e.g., asthma).

Misunderstanding of food allergy can result in unnecessary food restrictions or can become life threatening. Therefore, a thorough evaluation by a board-certified allergist should be recommended to distinguish food allergy from other medical disorders. Diagnostic steps include: thorough medical history to identify the suspected food; amount eaten to cause a reaction; amount of time between food consumption and development of symptoms; frequency of reaction; and other detailed information from a complete physical examination and laboratory tests.