Perianal streptococcal dermatitis is the presence of intense perianal erythema with or without scale that is caused by infection with group A beta-hemolytic Streptococci. Group B Streptococci and non-group A or group B Streptococci have been reported in some cases. It typically occurs between the ages of 6 months and 10 years. It has been rarely reported in adults. Some studies indicate a male predilection.

Accompanying symptoms may include perianal pruritus. Changes in bowel movements may also occur and may include painful defecation, blood noted in stools, or anal leakage of stool leading to constantly soiled undergarments. Systemic symptoms are absent.

Perianal streptococcal infection may be preceded by pharyngitis and can be a trigger for classic, inverse, or guttate psoriasis.