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Researchers at the Perelman School of Medicine at the University of Pennsylvania report that adults with seborrheic dermatitis in a large US cohort had a higher risk of having multiple epithelial barrier diseases in the skin, respiratory, gastrointestinal and ocular systems, and a lower risk of chronic obstructive pulmonary disease and pulmonary hypertension.
Seborrheic dermatitis affects oily areas of the skin and creates red, scaly patches that appear on the face, scalp, and other areas of high oil gland activity. This disease affects approximately 5% of the world’s population.
Background of the epithelial barrier
Previous studies have proposed mechanisms including colonization by the yeast Malassezia, lipase-mediated degradation of keratinocyte lipids, changes in the skin lipid matrix, and inflammation induced by downstream cytokines.
The epithelial barrier theory suggests that weakened barriers in the skin, respiratory tract, intestines or eyes allow germs, allergens and pollutants to pass through, stimulate the immune system and create lasting inflammation.
Previous electron microscopy findings on disorganized stratum corneum packing and functional studies showing increased transepidermal water loss also support barrier disruption in seborrheic dermatitis, while links to other respiratory, gastrointestinal, and ocular conditions remain unclear.
In the study “Epithelial barrier diseases in adult patients with seborrheic dermatitis,” published in JAMA DermatologyResearchers conducted a retrospective cohort study to explore the association between seborrheic dermatitis and epithelial barrier diseases.
Investigators used claims from several health centers and care facilities in the United States between 2016 and mid-2022. Among 20,274,189 patients, 733,776 individuals (3.62%) had at least one diagnosis of seborrheic dermatitis recorded.
The exposure was a diagnosis of seborrheic dermatitis recorded at any time during the observation window. Outcomes were diagnoses of epithelial barrier diseases during the same time period, also defined by at least one associated ICD-10 code. Negative control conditions with no known association with seborrheic dermatitis included hand fractures, sebaceous cysts, appendicitis, influenza, and astigmatism.
Main findings for all diseases
Strong positive associations emerged between seborrheic dermatitis and several dermatologic epithelial barrier diseases in fully adjusted models. Odds ratios (OR) included 3.21 for atopic dermatitis, 4.02 for alopecia areata, 2.25 for contact dermatitis, 3.26 for psoriasis, and 4.52 for rosacea.
Other positive associations included food allergy with an OR of 1.21, hidradenitis suppurativa 1.63, chronic spontaneous urticaria 1.35, pemphigus vulgaris 1.48, and bullous pemphigoid 1.60.
Beyond the skin surface, seborrheic dermatitis has shown positive associations with several epithelial barrier diseases. Rhinosinusitis had an OR of 1.24, celiac disease 1.36, irritable bowel syndrome 1.32, ocular allergy 1.39, and dry eye 1.48.
A higher prevalence of many of these conditions was observed in patients with seborrheic dermatitis compared to those without it. Associations with several other respiratory, gastrointestinal, and eye conditions, as well as hand fractures, appendicitis, influenza, and astigmatism, were within a predefined clinically insignificant range.
Interpretation and next steps
The authors interpret the clustering of seborrheic dermatitis with various inflammatory skin conditions involving various inflammatory markers and pathways as support for the epithelial barrier theory, suggesting that it is a “common driver in pathogenesis” and that epithelial dysfunction in seborrheic dermatitis may align with increased frequency of inflammatory skin diseases through multiple immunological pathways.
Positive associations with rhinosinusitis, celiac disease, irritable bowel syndrome, ocular allergy, and dry eye are presented as further support for a model in which disruption of an epithelial barrier may be linked to inflammatory conditions on other epithelial surfaces.
It is a bit of a leap from the comorbidity model to suggest directionality or any form of causality from epithelial barrier issues as a “shared driver,” although it is consistent with epithelial barrier theory.
Prospective, mechanistic studies are needed to determine whether skin barrier dysfunction is upstream, downstream, or simply concomitant with these other conditions and whether targeted interventions at the skin barrier can modify the risk of associated conditions elsewhere in the body.
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More information:
Sabrina Meng et al, Epithelial barrier diseases in adult patients with seborrheic dermatitis, JAMA Dermatology (2025). DOI: 10.1001/jamadermatol.2025.4313
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