Hidradenitis suppurativa (HS) is a chronic skin disease of the inverse areas of the body such as the axillary, inguinal, genital, and perineal regions. Estimates of the prevalence of HS ranges from 0.33% to 4%. This prevalence is partly based on large questionnaire-based studies. However, with these questionnaires, the severity of the disease could not be determined. In studies on acne, chronic hand dermatitis and rosacea, coloured pictures have been used as a guide to determine disease severity.This article is protected by copyright. All rights reserved.