BACKGROUND: Hidradenitis suppurativa (HS) and alopecia areata (AA) share similar inflammatory pathway and pro-inflammatory cytokines. However, the association between HS and AA was unclear. We aimed to evaluate the risk of incident AA among patients with HS. MATERIAL AND METHODS: We performed a multicenter cohort study by using the US Collaborative Network in the TriNetX Research Network. Patients with HS diagnosis were recruited and 1:1 propensity score matching was performed to identify the non-HS control group. Hazard ratio (HR) of AA in different sensitivity models were calculated within the follow-up periods. RESULTS: Comparing with non-HS controls, the risk of incident AA in HS patients was 1.79-fold higher (95% confidence interval (CI) 1.31-2.44) within 15-year follow up. Similar trends were observed in 3-year and 8-year follow up. For female HS patients, the risk of incident AA was 1.75-fold higher than non-HS female (95% CI 1.23-2.48). However, the trend was not observed in male HS patients (HR 1.52
95% CI 0.79-2.94). CONCLUSIONS: Patients with HS were associated with increased risk of incident AA. Clinicians should be aware of the observed association and the actual immunological interplay between the two diseases should be clarified in future lab-based studies.