Food allergies are a growing food safety and public health concern. A food allergy occurs when the body has an immune response to certain foods. The body's immune response can be severe and life-threatening, such as anaphylaxis.
While the immune system is usually protective, in people with food allergies, the immune system mistakenly responds to certain foods as if they are harmful.
In the U.S., there are eight food groups that account for 90 percent of severe allergic reactions, including milk, eggs, fish, crustacean shellfish, wheat, soy, peanuts, and tree nuts.
Sensitivity to particular foods can be indicated in a skin prick test or blood test. However, the results do not always show a true allergy unless there has been a previous reaction to the food.
A new study published in the journal Annals of Allergy, Asthma and Immunology - the publication of the American College of Allergy, Asthma, & Immunology - aimed to use data from a family-based food allergy study in Chicago, IL, to investigate patterns of food and airborne allergens in parents of children with food allergies.
Researchers found that only 28 percent of parents of children with food allergies tested positive to the foods to which they reported allergies.
"Parents of kids with food allergies had a higher rate of positive blood and skin tests to foods than the general population," says allergist Dr. Melanie Makhija, ACAAI member and co-lead author.
"But of the 2,477 parents, only 28 percent of those who self-reported a food allergy actually tested positive. 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. Allergy testing, including blood and skin prick testing, is not always reliable; there are a lot of false positives."
The team recruited local families from both hospital clinics and the community setting. To be eligible for inclusion in the study, parents had to have a child aged 0-21 years with a food allergy.
The child was considered to have a food allergy if they had positive skin test results teamed with symptoms typical of an allergic reaction to food within 2 hours of consumption. Symptoms included hives, difficulty breathing, wheezing, chest tightness, throat tightness, difficulty swallowing, fainting, and vomiting.
Peanut, milk, egg most common allergens in children
Of the total participants who responded to the questionnaire, 13.7 percent of parents reported having a food allergy. There were 3.6 percent of parents reporting allergy to shellfish, 2.1 percent to milk, 2.1 percent to peanut, 2.1 percent to tree nuts, 1.4 percent to fish, 1.1 percent to egg, 1.0 percent to soy, 0.9 percent to wheat, and 0.3 percent to sesame.
A total of 14.5 percent of mothers and 12.7 percent of fathers reported a food allergy. In their children, the most common allergen was peanut (37.3 percent), followed by milk (29 percent), and egg (22.1 percent).
"Previous studies have focused on the general adult population," says allergist Dr. Rachel Robison, co-lead author.
"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. 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."
Dr. Rachel Robison
"Interestingly, we also found that of the parents who reported no food allergy, 14 percent had positive tests to peanut and sesame, for example," she adds.
While skin tests may reveal sensitization, being sensitized to an allergen does not mean that you are necessarily allergic. Allergy blood tests alone are not as accurate as oral food challenges - considered the gold standard - in diagnosing allergies.
Patterns of allergen sensitization and self-reported allergic disease in parents of food allergic children, Melanie M. Makhija et al., Annals of Allergy, Asthma and Immunology, doi: http://dx.doi.org/10.1016/j.anai.2016.07.042, published online 12 October 2016.
ACAAI news release, accessed 11 October 2016 via Newswise.