Recently, two patients reported having eaten dairy products and experienced adverse reactions. One was a child who developed facial and lip swelling followed by generalized hives and respiratory distress, while the other was a young adult who noted abdominal cramps, bloating, and diarrhea. Only one was truly allergic to milk. Which do you think?

Adverse reactions to foods are a common complaint among patients who visit an allergist. One survey indicated that up to one-third of Americans felt they had a food “allergy,” but carefully done studies indicate that true food allergies occur in about 6-8% of children and 3-4% of adults. What, then, accounts for the difference? 

A food “allergy” is an abnormal reaction to a food that is immunologic in nature through a specific antibody immune reaction, generally to proteins contained in the food. The National Institute of Allergy and Infectious Diseases Guidelines for the diagnosis and management of food allergy define food allergy as “an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.”  The remainder of reactions to foods are termed “non-allergic,” and constitute the majority of food intolerances. These are far more common than true food allergy and may arise from a variety of sources including metabolic (lactose intolerance), non-allergic immunologic (Celiac Disease or gluten enteropathy), poisonings (scramboid poisoning with shellfish), pharmacologic (headaches from natural ingredients in chocolate), inflammatory (inflammation of the esophagus or food tube with specific white blood cells called “eosinphils”), neurofunctional (food-induced cramps and bloating in irritable bowel syndrome), toxins (aflatoxins in grains and cereals), and more.

Distinguishing a true food allergy from other adverse reactions to foods is based on the history of the reaction (true allergic reactions are typically immediate and involve respiratory membranes, skin or GI tract), the particular food suspected to provoke the reaction (some foods are more allergenic than others, although any food can provoke an allergic response), how the food was prepared and served (cooking tends to reduce the likelihood of some allergic responses, and cross-contamination at a buffet, restaurant, etc), the amount of food ingested (allergic reactions generally occur with sometimes even trace amounts), reproducibility (have similar symptoms occurred when the food was eaten previously), amount of food ingested (allergic reactions may occur when even trace amounts are eaten), amount of time from ingestion to reaction (allergic reactions tend to occur immediately or after a short duration), food aversions (some young children cannot vocalize minor reactions but know they don’t like certain foods and will avoid them). Some food allergies may occur only when food ingestion is coupled with exercise shortly after, and in some, certain foods cannot be eaten during a pollen season.

If you have specific food intolerances, and suspect a food allergy may be involved, and depending on the acuteness and severity of reaction, it would be helpful to see an allergist. You should come prepared to report the exact symptoms you experienced, in what setting the food was consumed, the timing and duration of the reaction, a complete list of foods ingested shortly before the reaction (including packaged ingredients in sauces, dressings, mixes), and what treatment was required. Your allergist can do specific testing to determine if a true food allergy is present, and if so, instruct you on proper treatment including avoidance, prevention, and specific medications.