Commercial apple extracts (AEs) do not show satisfactory sensitivity in diagnostic procedures, and SPTs with fresh apple (prick-to-prick) proved to be more sensitive in confirming a history of apple-induced OAS.3 However, the content of Mal d 1 varies in different apple strains4 and is additionally affected by postharvest storage conditions.5 Hence prick-to-prick testing with fresh apple cannot be regarded as a standardized diagnostic procedure. Because rMal d 1 can be produced in defined and consistent qualities and quantities, it might improve the sensitivity of diagnostic tests for apple allergy. Considering a mean wheal diameter of 3 mm or larger as positive, all patients showed skin reactivity to rBet v 1, and 20 of 21 patients had positive reactions to BPE (Table I). ...in accordance with previous data, rBet v 1 was more sensitive than BPE in SPTs (100% and 95.2%, respectively) to diagnose birch pollen allergy.7 Wheal sizes induced by rBet v 1 were significantly larger than those induced by BPE (P = .001, Wilcoxon signed-rank test). rMal d 1 induced dose-dependent skin reactions in patients with apple allergy (Fig 1, A).