Background Data on the frequency of resolution of anaphylaxis to foods are not available, but such resolution is generally assumed to be rare.
Objective To determine whether the frequency of negative challenge tests in children with a history of anaphylaxis to foods is frequent enough to warrant challenge testing to re-evaluate the diagnosis of anaphylaxis, and to document the safety of this procedure.
Methods All children (n=441) who underwent a double-blind, placebo-controlled food challenge (DBPCFC) between January 2003 and March 2007 were screened for symptoms of anaphylaxis to food by history. Anaphylaxis was defined as symptoms and signs of cardiovascular instability, occurring within 2 h after ingestion of the suspected food.
Results Twenty-one children were enrolled (median age 6.1 years, range 0.8–14.4). The median time interval between the most recent anaphylactic reaction and the DBPCFC was 4.25 years, range 0.3–12.8. Twenty-one DBPCFCs were performed in 21 children. Eighteen of 21 children were sensitized to the food in question. Six DBPCFCs were negative (29%): three for cows milk, one for egg, one for peanut, and one for wheat. In the positive DBPCFCs, no severe reactions occurred, and epinephrine administration was not required.
Conclusions This is the first study using DBPCFCs in a consecutive series of children with a history of anaphylaxis to foods, and no indications in dietary history that the food allergy had been resolved. Our study shows that in such children having specific IgE levels below established cut-off levels reported in other studies predicting positive challenge outcomes, re-evaluation of clinical reactivity to food by DBPCFC should be considered, even when there are no indications in history that anaphylaxis has resolved. DBPCFCs can be performed safely in these children, although there is a potential risk for severe reactions.