Food allergies aren’t as family-inclusive as we think, suggests a new study published in the Annals of Allergy, Asthma and Immunology.

Researchers recruited more than 2,000 parents of children with food allergies from the Chicago area to undergo their own food allergy tests, which included a skin prick and blood test. Prior to the tests, the parents were asked if they had a food allergy, and 13.7 percent reported that they did. Come test time, though, less than one-third of these parents tested positive for the specific allergies they said they had.

“Parents of kids with food allergies had a higher rate of positive blood and skin tests to foods than the general population," said lead author Dr. Melanie Makhija, an assistant Professor of Allergy and Immunology at the Northwestern University Feinberg School of Medicine, in a statement. "But of the 2,477 parents, only 28 percent of those who self-reported a food allergy actually tested positive.”

The disconnect between parents’ perceptions and reality may have several reasons, Makhija further explained.

“This tells us that either people haven't been tested and are assuming an allergy from a previous reaction to a food, or they haven't been tested properly and may not truly have an allergy,” she said. “Allergy testing, including blood and skin prick testing, are not always reliable; there are a lot of false positives."

The researchers found additional evidence for this when they looked at the volunteers’ levels of antibodies (IgE) in their blood.

“While we found positive test results were more common in parents of kids with food allergies, the actual levels in the blood for the foods were quite low,” said co-author Dr. Rachel Robison. “Low positives in allergy testing are more likely to be false positives. This points to the importance of proper testing for any kind of allergy, but particularly food allergies.”

The team also found that parents sometimes underestimated their allergy risk. Robinson noted that “of the parents who reported no food allergy, 14 percent had positive tests to peanut and sesame."

The most reliable means of testing for food allergy currently is to have someone eat a suspected food in slowly increasing doses under the close supervision of a medical professional, otherwise known as an oral food challenge.

It’s estimated that 8 percent of children under the age of 18 have a food allergy, according to the American Academy of Allergy, Asthma & Immunology.

Source: Makhija M ,Robinson R, Caruso D, et al. Patterns Of Allergen Sensitization And Self-reported Allergic Disease In Parents Of Food Allergic Children. Annals of Allergy, Asthma and Immunology. 2016.