Fixed drug eruptions due to co-trimoxazole

Co-trimoxazole is a less common cause of fixed drug eruption (FDE). The offending drug is usually sulfamethoxazole but reactions to trimethoprim have been reported. Fixed drug eruption is uncommon in children compared to adults as the drugs most commonly responsible are seldom or never used in children. We report four patients with FDE to co-trimoxazole, three of whom were children. All were given the offending drug for upper respiratory tract infections. Each of the patients had several episodes of FDE before the diagnosis was suspected. The patients, as well as the general practitioners, initially thought that the skin lesions were related to the infections rather than the drugs. One of the patients had FDE to trimethoprim and the intensity of his reaction appeared to be dose-related. As co-trimoxazole is being used more commonly, we would expect to see more FDE, even among the paediatric age group.