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Background: Alopecia areata (AA) has features of both autoimmune and atopic pathogenesis, but information on the risk of people with AA developing autoimmune and atopic conditions is limited., Objective: To assess the prevalence and incidence of atopic and autoimmune conditions in people with AA., Methods: This was a population-based cohort study of 8051 adults with newly diagnosed AA (AA group) and 32 204 adults in the matched control group, using the UK Oxford-Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) network primary care database, 2009-2018 (trial registration number: NCT04239521). Baseline prevalence of common atopic and autoimmune conditions, and risk of new-onset atopic and autoimmune disease, were estimated., Results: Atopic and autoimmune conditions were more prevalent in the AA group than the control group (atopic 37.2% vs. 26.7%, autoimmune 11.5% vs. 7.9%). The AA group were 43% more likely to develop any new-onset atopic condition [adjusted hazard ratio (aHR) 1.43. 95% confidence interval (CI) 1.28-1.61] and 45% more likely to develop any autoimmune condition (aHR 1.45, 95% CI 1.28-1.66) compared with the control group. When examining individual conditions, the AA group were at increased risk of atopic dermatitis (aHR 1.91, 95% CI 1.67-2.19), allergic rhinitis (aHR 1.32, 95% CI 1.14-1.54), autoimmune hypothyroidism (aHR 1.65, 95% CI 1.35-2.02), systemic lupus erythematosus (aHR 4.51, 95% CI 1.88-10.82) and vitiligo (aHR 2.39, 95% CI 1.49-3.82). There was no evidence for a higher incidence of other conditions examined., Conclusion: People with AA have an increased burden of atopic and autoimmune comorbidity. This supports previous work suggesting that both T helper cell (Th)1 and Th2 immune responses may be implicated in the pathogenesis of AA., Competing Interests: Conflict of interest S.deL. is Director of RCGP RSC, he had received funding for projects from Eli Lilly, Astra Zeneca, GSK, MSD, Seqirus, Daiichi Sankyo and Takeda – all through his universities and none related to this study. W.S.C. is an employee of Pfizer Ltd. S.H. and C.T. are investigators on the Pfizer-funded ALLEGRO clinical trial. S.H., M.H., A.E.M. and A.G.M. are members of the British Association of Dermatologists guidelines group for alopecia areata., (© The Author(s) 2022. Published by Oxford University Press on behalf of British Association of Dermatologists.)

Background: It is not known whether alopecia areata (AA) is associated with a greater or reduced risk for infection., Aim: We undertook a population-based study exploring associations between AA and common infections., Methods: We extracted primary care records from the UK Oxford-Royal College of General Practitioners Research and Surveillance Centre database (trial registration: NCT04239521). The incidence of common and viral infection composite outcomes, and individual respiratory, gastrointestinal (GI), skin, urinary tract, genital and herpes infections, were compared in people with AA (AA group, n = 10 391) and a propensity-matched control group (n = 41 564). Adjusted hazard ratios (aHRs), controlling for sociodemographic and clinical covariates, and comorbidities were used to estimate the association between AA and each infection over 5 years., Results: The incidence (per 100 person-years) of common infections was slightly higher in the AA group [14.2, 95% confidence interval (CI) 13.8-14.6] than the control group (11.7, 95% CI 11.5-11.9). In adjusted analysis, positive associations were observed for composite outcomes (common infections aHR 1.13, 95% CI 1.09-1.17; viral infections aHR 1.11, 95% CI 1.07-1.16) and with respiratory tract, GI, skin and herpes simplex infections (aHR range 1.09-1.32). Excluding people in the control group without a recent consultation with their general practitioner showed no association between AA and infection (common infections aHR 1.01, 95% CI 0.98-1.05, viral infections aHR 0.99, 95% CI 0.95-1.03)., Conclusions: The association between AA and common infection may represent a higher propensity of people with AA to engage with healthcare services (and thereby to have infections recorded), rather than a true association between AA and infection. Overall our findings suggest that AA is not associated with a clinically significantly increased or decreased incidence of common infections., Competing Interests: Conflict of interest S.deL. is Director of RCGP RSC, he has received funding for projects from Astra Zeneca, Daiichi Sankyo, Eli Lilly, GSK, MSD, Nova Nordisk, Seqirus and Takeda – all through his universities and none related to this study. W.S.C. is an employee of Pfizer Ltd. S.H. and A.G.M. have undertaken paid consultancy for Pfizer. S.H. and C.T. are investigators on the Pfizer-funded ALLEGRO clinical trial. A.G.M., M.H., A.E.M. and S.H. are members of the British Association of Dermatologists guidelines group for alopecia areata., (© The Author(s) 2022. Published by Oxford University Press on behalf of British Association of Dermatologists.)

Competing Interests: Conflict of interest SMM is a sub-investigator and CT is a principal and (national) chief investigator on the Pfizer-funded ALLEGRO clinical trial in alopecia areata. CT also provides consulting services to Pfizer; sits on the scientific advisory board of Zura Bio Limited and has received speaker fees from Leo Pharma. The other authors declare that they have no conflict of ­interest.