ObjectivePerianal streptococcal dermatitis (PSD) in adults is still not well documented. After demonstrating systemic therapy to be efficient in adultsanalogous to the therapeutic approach to the well-known disease in childrenthe question remained whether local therapy is also sufficient. We therefore treated adult PSD patients with mupirocin 2% locally.Patients and methodsAfter diagnosis, patients were treated with mupirocin 2% locally for 2weeks. Additional concomitant anorectal diseases were treated according to standard guidelines and the patients' clinical course was followed. Acontrol group of patients without erythema, eczema or other symptoms of PSD was examined for the presence of -haemolysing Streptococci (BHS) by perianal swab in order to investigate the prevalence of asymptomatic colonization. Demographic and microbiological data were assessed and compared between and within treatment and control groups.Results129 PSD patients >17years (mean48years) were diagnosed between February 2012 and March 2014. In most cases, groupB BHS (GBBHS) were found. In 99patients, local treatment was administered for 14days. In 69 of 75patients (92%) with apost-treatment swab, this swab was negative. Whereas 35patients (35.4%) had no further anorectal complaints, 57patients (57.6%) required continuing treatment of their concomitant anorectal disease. In the control group, GBBHS were found in 10%.ConclusionPSD should be included into differential diagnoses of refractory eczema in adult patients and is mainly caused by GBBHS. As alocal skin infection, PSD can be treated effectively with mupirocin 2% locally. However, pregnant women, immunodeficient patients as well as patients with systemic signs and symptoms of infection must be addressed differently and asystemic therapy remains standard in these special cases.What does this paper add to the literature?This paper sheds new light on the treatment concept of perianal streptococcal dermatitis, up to now recognized as adisease of children. As aresult of this paper, adult patients with persisting eczema despite proper anorectal treatment should be screened routinely for perianal streptococcal dermatitis and can be treated locally.