[Study of drug allergies with special reference to skin manifestations]

One hundred and forty four patients, with dermal reactions to different drugs, were chosen from our clinic. The selection criteria was based on a detailed and careful anamnesis in order to be certain of the specific drug responsible for the reaction. We tried to establish a drug-specific reaction pattern for each of the drugs studied. Intradermal skin tests were performed with all drugs to be studied, except with pyrazolones and aspirin, for which patch tests were applied. The drug concentrations were established prior to the tests in order to avoid unwanted unspecific reactions. In every case, immediate and delayed reaction readings were carried out. A three crosses reaction (+++) was considered positive. The skin tests were positive in 44% of the cases, a value higher than those referred to by most authors. The delayed reactions to skin tests and the chloramphenicol-mediated delayed-type "dermatitis-like" manifestations are compared. It is noteworthy to mention that positive delayed reactions were observed more frequently with chloramphenicol than with any of the other studied drugs. The same applies for those patients with a positive history to chloramphenicol. The most common reaction pattern to penicillin and streptomycin in our series (20%) were urticaria and Quincke's edema. Penicillin, pyrazolones and streptomycin were the most common drugs responsible for urticarial patterns, being the pyrazolones related to fixed erythema in many cases. The age group 25-50 was the most frequently involved. No sex predominance was observed. The value of the classic skin tests is discussed, so are history recording and the in vitro tests.