Purpose of the Study
The authors set out to determine the role and appropriate evaluation of food hypersensitivity in atopic dermatitis, using prick tests with a limited number of foods.
One hundred sixty-five children, ages 4 months to 21.9 years, who met the criteria for a diagnosis of atopic dermatitis (AD), were enrolled in the study conducted in the pediatric allergy clinic of a teaching hospital.
Precise histories were obtained as well as complete physical examinations. All patients underwent allergy prick tests with at least 12 common food antigens plus other foods that the parents thought caused symptoms. Food challenges were carried out on the basis of a positive skin test after the suspected food was eliminated for 2 to 3 weeks. A double-blind, placebo-controlled, food challenge (DBPCFC) was the method used. No child with a convincing history of a major anaphylactic reaction to a specific food was challenged with that food.
A staggering 92% of these children had a family history of allergic rhinitis, asthma or AD! There were 2061 prick tests to foods performed with 323 (15.6%) read as positive. Ninety-eight patients had at least 1 positive test while 67 were completely negative. A total of 266 DBPCFC were performed and 88 were positive, plus an additional 22 were not performed because of a history of anaphylaxis. The results showed that a positive skin test had 100% sensitivity, 66% specificity, 65% positive predictive value, and 100% negative predictive value. The seven foods that accounted for 89% of the positive challenges were milk, egg, peanut, soy, wheat, cod/catfish, and cashew.
Any child with significant AD who has been treated with the standard topical protocols plus systemic antihistamines and who fails to adequately respond should be considered for limited food prick skin testing, eg, the seven above. Elimination and challenge should be tried and if positive, an elimination diet should be instituted.
We all encounter those children with tough to treat AD. The authors most convincingly present their case for a limited food skin test screening program. Your local friendly allergist may therefore be the best person to consult regarding your next troublesome AD patient. Rubbing “stuff” on and gulping pills does have it's limits, especially with the dramatic benefits that can be observed when food allergies are identified and appropriate diets are instituted.