Perianal streptococcal dermatitis is a relatively common disease. The clinical picture is fairly typical, with bright red skin around the anus. Bacterial culture confirms the clinical diagnosis. Oral antibiotics are needed for cure. The main confusing diagnosis is candidal infection. If both group A pyogenic streptococcus and Candida albicans are found simultaneously, the latter is probably saprophytic; treat the streptococcus.