A LARGE U.S. study has found that people with seborrheic dermatitis (SD), a common inflammatory skin condition, are significantly more likely to develop other diseases involving epithelial barrier dysfunction, supporting the epithelial barrier theory (EBT) that damage to protective tissue layers can contribute to multiple disorders across the body.
Seborrheic Dermatitis and Epithelial Barrier Diseases: A Two-way Relationship
In this retrospective cohort study, researchers analysed medical records from over 5 million patients between 2016 and 2022 from a large US administrative claims database. They discovered strong, two-way links between SD and a range of epithelial barrier diseases (EBDs) using multivariable Cox proportional hazard models.
The risk of developing SD was significantly higher in people who already had other barrier-related conditions. For example, the hazard ratio (HR) for SD following alopecia areata was 3.47 (95% CI: 3.24–3.71), psoriasis was 2.62 (2.54–2.69), rosacea was 2.84 (2.78–2.90), and atopic dermatitis was 2.46 (2.40–2.53). More modest but still significant associations were found for contact dermatitis [1.92 (1.88–1.96)], hidradenitis suppurativa [1.79 (1.63–1.97)], and several non-skin conditions, including rhinosinusitis [1.34 (1.32–1.35)], food allergy [1.47 (1.42–1.54)], celiac disease [1.55 (1.43–1.68)], ocular allergy [1.55 (1.49–1.61)], and dry eye [1.54 (1.52–1.56)].
The reverse analysis showed similar trends. People with SD faced increased risks of later developing other EBDs, most notably psoriasis [3.52 (3.42–3.61)], rosacea [2.85 (2.79–2.92)], and alopecia areata [2.81 (2.61–3.03)].
Implications for the Epithelial Barrier Theory and Future Care
The findings provide robust, population-level evidence supporting the epithelial barrier theory, that disruptions in epithelial barriers contribute to a cascade of inflammatory diseases, both locally and at distant sites. Seborrheic dermatitis may therefore serve as a marker for broader epithelial vulnerability, allowing future prevention and treatment strategies that aim to strengthen epithelial barriers.
This study reinforces the epithelial barrier theory, highlighting seborrheic dermatitis as both a consequence and predictor of barrier dysfunction, underscoring the need for barrier-focused prevention strategies.
Reference:
Meng S et al. Bidirectional Associations Between Seborrheic Dermatitis and Epithelial Barrier Diseases: A Retrospective Cohort Study. Allergy. 2025; DOI: 10.1111/all.70112.
