Cutaneous accidents due to sulfonamides have been known since 1939 and their frequency is about 1%. Allergy to a sulfonamide definitely excludes the use of all the others and causes allergy to the amine group in para: anaesthesia of the procaine type, PAS, aniline dyes, synthetic sweeteners, and hair dyes. There is no correlation between the amount ingested and the severity of the accidents. Clinically, these accidents are very polymorphous ranging from photosensitization to eruptions as serious as acute epidermal necrosis.