Eliciting doses of positive challenge test in cow's milk allergy are related to cow's milk specific IgE levels.

BACKGROUND Ingestion of small amounts of cow's milk (CM) can elicit adverse reactions in patients with IgE-mediated CM allergy. Knowing the dose eliciting allergic reactions and the factors affecting it can be of great help in avoiding these reactions. OBJECTIVE To analyse the eliciting doses of positive challenge test in patients with CM allergy and to determine its association with the level of CM specific IgE. METHODS Ninety-eight positive challenge tests in 56 children, median age of 11 months (3-80) with IgE-mediated CM allergy were retrospectively analysed. Open oral challenge tests were carried out by gradually increasing doses of milk (2-100 ml). The relationship between challenge test doses and CM specific IgE levels were studied. RESULTS 18 % of the challenge tests were positive with 2 ml, 24 % with doses between 5 and 10 ml, and the other 58 % with doses between 25 and 100 ml. An inverse association between the doses of the positive challenge test and the level of CM specific- IgE was found, 13.9 kU/L (0.54-> 100 kU/L) when the challenge test was positive with the smaller dose (2 ml); and 1.73 kU/L (< 0.35-76.4 kU/L) with doses above 2 ml (p = 0.0001). The median age of the patients was 13 months (6-49) when the challenge test was positive with 2 ml vs 9 months (3-80) with doses above 2 ml (p = 0.048). CONCLUSION The CM specific IgE level and patient's age should be considered in the assessment of the eliciting doses of positive challenge test in CM allergy.