Severe delayed-onset hypersensitivity reactions to amoxicillin in children.

Amoxicillin, a semisynthetic aminopenicillin, has achieved widespread use in recent years for the treatment of respiratory tract and otic infections. Serious reactions have been relatively infrequent. From July 1986 to June 1987, 11 children aged 6 months to 10 years presented with delayed-onset hypersensitivity reactions. In 10 the symptoms were consistent with a serum-sickness-like illness, including urticaria, angioedema, arthritis and arthralgia. Radioallergosorbent testing for IgE antibodies to penicillin yielded negative results, and lymphocyte transformation testing gave a positive result in only one patient. Because of the negative immunologic test results and the occurrence of reactions only in children, who had received an amoxicillin solution, the reactions may have been caused by the excipient.