A 24 year-old man developed an anaphylactic reaction within thirty minutes of an oral administration of penicillin V. He suffered from recurrent streptococal pharyngitis that was usually treated with penicillin V with good tolerance.
Skin prick and intradermal tests with penicilloyl-polylysine, minor determinant mixture, amoxicillin, ampicillin and cefuroxima were negative. However, a skin prick test with penicillin V was positive in the patient and negative in 10 controls. Determination of specific (Immunogloblulin (Ig) E to penicillin V was 0.64 kU/L. Specific IgE to penicillin G, amoxicillin and ampicillin were all negative. Single blind controlled oral challenge with amoxicillin and cefuroxime were both negative.
This is an exceptional case of an anaphylactic reaction induced by phenoxy-methylpenicillin with positive allergologic study in vivo and in vitro tests and with negative allergological study to other β-lactams.

Key words: β-lactams. Hypersensitivity. Penicillin V. Penilevel