Challenge program in the patients with previous positive specific IgE to penicillins. (A) Challenge program within each visit. (B) Program for measurements of specific IgE to penicillins. In continuation of each challenge, specific IgE measurements were performed and repeated 4 weeks later. In case of any positive clinical reaction or renewed positive specific IgE, further challenges were terminated. Visit -1: The visit of the first positive measurement of specific IgE to penicillin. Visit 0: The visit of the first negative measurement of specific IgE to penicillin. Pen G: Benzylpenicillin, Pen V: Phenoxymethylpenicillin, p.o.7: prolonged oral challenge with penicillin for 7 days, IgE: specific immunoglobulin E to penicillins (Pen G, Pen V, ampicillin, amoxicillin). All patients had negative specific IgE to penicillin at the time of penicillin challenge (visit 0 and 1).