Any food can cause an allergic reaction, but 90 percent of the time one of the “Big Eight” foods—milk, eggs, peanuts, tree nuts, wheat, soy, fish or shellfish—is the trigger. Allergists and immunologists don’t understand why these foods cause a reaction, nor do they know exactly what leads someone to develop a food allergy. There does, however, appear to be a genetic component, as studies show those who suffer from hay fever, or asthma, or who have family members with allergies, are more likely to develop food allergies.
Still, anyone can develop a food allergy, at any time, says Scott Sicherer, M.D., associate professor of pediatrics at the Jaffe Food Allergy Institute at Mount Sinai in New York and author of Understanding and Managing Your Child’s Food Allergies (Johns Hopkins Press, 2006). Some allergies—including milk, eggs, soy and wheat allergies—appear more often during childhood, and many kids outgrow them. Others, like shellfish allergies, tend to develop during adulthood. Such is the highly individual (and unpredictable) nature of the food-allergy beast.
Many people mistake localized discomfort, say a rumbling tummy after eating certain foods, as a food allergy, but it’s generally not. In fact, according to Dr. Sicherer, “Roughly 20 percent of people think they have food allergies, but the majority of them don’t.” They may, for example, have suffered a single bout of food poisoning or have trouble digesting certain sugars, but these don’t fall under the food-allergy umbrella. Knowing the difference is often tricky, which is why consulting a doctor is so important.
For instance, milk is one food to which people can either be allergic or intolerant (or both), so it’s useful for highlighting the difference between the two terms. When the milk’s protein triggers an immune reaction like hives or breathing problems, this is usually a milk allergy. But when a person can’t digest the milk’s sugars (often causing loose stools), this is usually lactose intolerance.