Bidirectional Association Between Irritable Bowel Syndrome and Dermatological Disease: A Large-Scale Retrospective Study

Background/Objectives: Microbial dysbiosis is implicated with a pathogenic role in both irritable bowel syndrome (IBS) and several dermatological conditions. Yet, few studies have assessed a potential overlapping epidemiologic association. We aimed to assess the 1-year prevalence of common dermatologic conditions following an initial IBS diagnosis and to evaluate the reverse association using reciprocal analyses; Methods: We conducted a retrospective study using TriNetX. Patients aged 18-50 with no history of inflammatory bowel disease, celiac disease or infectious intestinal disease were matched 1:1 to healthy controls by demographics and comorbidities. The primary outcome was the prevalence of acne vulgaris, psoriasis, atopic dermatitis, hidradenitis suppurativa, rosacea, vitiligo, alopecia areata, urticaria, 1-year after IBS diagnosis, measured using Odds Ratios (OR) and 95% confidence intervals. To confirm bidirectionality, reciprocal analyses were performed; Results: Over a 1-year period, IBS patients were less likely to have acne vulgaris (OR: 0.78, CIs: 0.75-0.80) and vitiligo (OR: 0.78, CIs: 0.64-0.95) compared to those without. IBS pa-tients were more likely to have psoriasis (OR: 1.14, CIs: 1.08-1.21), hidradenitis suppurativa (OR: 1.11, CIs: 1.03-1.20), rosacea (OR: 1.10, CIs: 1.03-1.18), and urticaria (OR: 1.27, CIs: 1.21-1.34) com-pared to healthy controls. No association was found for atopic dermatitis or alopecia areata. In the reciprocal analysis, alopecia areata patients (OR: 0.76, CIs: 0.64-0.90) had a lower prevalence of IBS compared to healthy controls. IBS was shown to occur more frequently in patients with psoriasis (OR: 1.15, CIs: 1.07-1.23), rosacea (OR: 1.23, CIs: 1.15-1.31), and urticaria (OR: 1.06, CIs: 1.01-1.12) compared to healthy controls. No association was seen in patients with acne, atopic dermatitis, hidradenitis suppurativa, and vitiligo; Conclusions: IBS shows a bilateral positive overlapping association with psoriasis, rosacea and urticaria. Hidradenitis suppurativa showed a positive association only among IBS patients, with no reciprocal relationship. Moreover, our findings suggest that acne and vitiligo were inversely associated with IBS, however this was not supported in our reciprocal analysis. Although no association was initially found between IBS and alopecia areata, the reciprocal analysis suggests a potential inverse association. No association was seen with atopic dermatitis bilaterally. Clinicians who treat these disorders should be aware of the potential bidirectional association.