In a new study 1120 children whose siblings were diagnosed with food allergy were tested with skin prick tests, food specific blood tests and review of clinical history of food reactions. What the study revealed was that 53% of the siblings had food sensitivity (that is, a non-allergic reaction to food), and only 13 percent had definite food allergy according to the new research presented at the annual meeting of the American College of Allergy, Asthma & Immunology in San Antonio, Texas in November, 2015.
All too often, parents are concerned that because one child has food allergies, their siblings probably do, too. Children inherit the ability to be allergic, but not an allergy to specific foods or inhalants. For example, in one family the mother may be allergic to ragweed and penicillin, the father allergic to shrimp, oak trees and grass and a child allergic to peanuts, cats and dust mites. Specific allergy does not breed true in families. The new study provides good evidence supporting this idea. Food allergy testing should not be used to predict potential risks in order to make a diagnosis; rather, it should be used to help confirm a diagnosis.
“A large proportion of these parents are unnecessarily avoiding a food their child could eat,” says Ruchi Gupta, lead author on the study and an associate professor of pediatrics at Northwestern University Feinberg School of Medicine. False positives cause unnecessary stress and fear for parents and children, and, somewhat paradoxically, could increase the risk of a real allergy: Avoiding a potential allergen may increase the risk of developing food allergies later in life.”
The most important question in diagnosing food allergy is whether the child has tolerated the food in the past. While some severe allergies are obvious, parents given a positive blood test result should seek advice from an experienced allergist who performs medically supervised “food challenge” tests, the gold standard for diagnosing food allergy.
Even when a food allergy has been confirmed, parents should continue to work with their allergist, because some allergies are outgrown, particularly allergy to milk, eggs, soy and wheat. There are strategies that work for some children, to increase the likelihood that milk and egg allergy will be outgrown. Some centers provide treatment for food allergy that dramatically reduces the risk of a reaction and allows many patients to eat their problem food without difficulty.
Misdiagnoses of food allergies can have lasting effects, ranging from anxiety to unnecessary dietary limitations. Sometimes the unnecessary dietary limitations can lead to malnutrition. Over-diagnoses can also trivialize the severity of life-threatening, immune-mediated food allergies which account for about 150 deaths in the U.S. each year. Still, blood and skin tests remain the most frequently used methods of diagnosis.
The best approach is to limit food allergy testing to those foods likely to cause an allergic reaction based on the history of problems. Many problems attributed to food allergy by the public and even some physicians don’t have the features of a true allergic reaction at all.