The American College of Allergy, Asthma and Immunology (ACAAI) met for its Annual Scientific Meeting in Houston last week (November 7-11) and heard that OFCs, in which a person is given a small dose of food to test for a severe reaction, is far more accurate than a skin or blood test when it comes to food allergy testing.
Delegates heard about two cases evidencing the risks of misdiagnosis and even showing how a lack of accurate testing can lead to increased allergies.
The right treatment
One case involved a 17-month-old boy with atopic dermatitis (eczema) and what was thought to be peanut allergy based on a skin test and blood test. The boy had two prior small rashes on his mouth after eating peanut.
"We weren't convinced he was allergic to peanut because although his prior skin prick and blood testing suggested he was sensitive to peanut, he'd never had a convincing allergic reaction," said allergist Katherine Tison, MD, ACAAI member and lead author of the study.
"We performed an OFC, and he passed with only a small rash on his face which resolved itself. That showed he was sensitive to peanut, but not allergic. The case shows that an OFC should be used to determine if a child is truly allergic, especially prior to starting oral immunotherapy treatment, which was being considered for this child. A sensitivity shown through a skin prick or blood test is not enough to diagnose a food allergy."
Following the successful OFC, the allergists encouraged the parents to begin giving the child peanut products three times weekly to maintain his tolerance to peanut.
Aczema turns to allergy
The second case concerned a three-year-old boy with uncontrolled atopic dermatitis (eczema) and asthma whose eczema hadn't been properly treated.
Because children with eczema often later develop food allergies, parents sometimes decide to avoid foods that have previously been tolerated due to concerns about flares of eczema—or concerns about developing a full-blown food allergy.
"Skin prick testing showed the little boy had sensitisation to egg, peanut and sesame," says allergist Evelyn Wang, MD, ACAAI member and lead author of the abstract.
"Despite him tolerating the foods previously, and no clear association between eating the foods and flares of his eczema, his parents removed these items from his diet for one year. After one year, he passed an OFC to egg and sesame, but experienced anaphylaxis to peanut. The case shows it is possible that removing foods from a child's diet in the hope of improving eczema may lead to food allergy later in life."
The authors of the abstract point out that it's important that good skin care and appropriate topical treatments for eczema be tried first to help determine if an eczema flare is due to a food allergy. If, after this treatment, the eczema flare continues, then they say it makes sense to move onto an OFC to determine if food allergy is the cause.