Evaluation of the Skin Test Reactions in Patients with Delayed Type Rash Induced by Penicillins and Cephalosporins

Skin test reactions were evaluated in 39 patients with delayed type generalized drug eruptions in which penicillins (PCs) or cephalosporins (CSs) were proved to be the causative drugs by intradermal testing and provocation. They were also compared with the experimental PC/CS rash of guinea pigs reported previously. The skin test was positive in 37 (95%) of 39 patients tested and in 13 (87%) of 15 patients, in whom the causative drugs were identified by provocation, in which intradermal testing with 2 to 10% PC/CS in saline solution was employed and the skin test reaction was observed not only 24 hours later but also 6 to 9 hours later. It is considered that the skin test is a valuable in vivo test for the diagnosis of drug allergy. From the skin test reaction, it appears that the PC/CS rash is classified into at least two different reactions, the Jones‐Mote type reaction and the tuberculin type reaction. No cross reactions between PC and CS derivatives were observed in either the skin testing or the provocation in man, which is the same pattern seen in the animal model. Cross reactions among the PC derivatives in man were not found as frequently as expected from the results in animals.