Generalized erythematous skin eruptions due to trimethoprim itself and co-trimoxazole

A 20-year-old Japanese woman (Case 1) and a 70-year-old Japanese man (Case 2) consulted us with slight fever and disseminated erythematous papules. Examinations revealed that the first case was a skin eruption due to trimethoprim itself and the second was due to both trimethoprim and sulphamethoxazole. To our knowledge, our Case 1 is the first reported case with an erythematous papular type skin eruption caused by trimethoprim itself, and our Case 2 is the first case of a skin eruption in reaction to both trimethoprim and sulphamethoxazole.