BACKGROUND: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease characterized by recurrent inflamed nodules. No pathognomonic test is available for HS; hence the diagnosis is based on three clinical criteria.

OBJECTIVES: To estimate the cross-sectional prevalence and characterize patients with HS in the Danish Blood Donor Study cohort.

METHODS: A questionnaire previously developed containing HS screening questions, the Major Depression Inventory, the Short Form-12, as well as questions about height, weight and drinking habits was answered by 27 765 blood donors.

RESULTS: The prevalence of HS was 1·8% [95% confidence interval (CI) 1·6-2·0%] in the cohort of Danish blood donors. Donors with HS were on average 4·7 years younger (P < 0·001), had 1·3 kg m -2 higher mean body mass index (BMI) (P < 0·001) and were significantly more likely to smoke [odds ratio (OR) 1·44, 17·9% vs. 13·1%, P = 0·002] compared with donors without HS. Furthermore, significantly more donors with HS were classified as having moderate depression (3·2% vs. 0·7%, P < 0·001). Also, significantly more patients with HS were apprenticeship educated, received educational support and sickness or cash benefits.

CONCLUSIONS: The prevalence of HS in the cohort of blood donors was estimated to 1·8% (95% CI 1·6-2·0%). Donors with HS reported characteristics similar to those reported for hospital-based patients with HS such as higher BMI, smoking rates and lower socioeconomic status than donors without HS.