Seborrheic dermatitis linked to systemic barrier breakdown

Study of 20 million adults reveals shared pathways between skin, gut and ocular inflammation.

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Seborrheic dermatitis, a common and chronic inflammatory skin disorder, has long been recognised for its characteristic erythematous, greasy scaling across sebaceous-rich areas of the face and scalp.

Affecting around 5% of the global population, it remains a persistent challenge for dermatologists due to its relapsing nature and unclear pathogenesis.

Now a massive cohort study, published in JAMA Dermatology, links seborrheic dermatitis to a range of other inflammatory conditions affecting the skin, gut, eyes and respiratory tract, offering some of the strongest real-world evidence yet for the epithelial barrier theory of disease.

The findings suggest that when the skin’s defences break down, the ripple effects may extend far beyond the scalp or face, hinting at a systemic process that connects seemingly unrelated disorders through shared mechanisms of barrier disruption and chronic inflammation.

Using data from Optum’s Clinformatics Data Mart Database between 2016 and 2022, researchers followed more than 20 million adults with an average of 3.5 years of observation – effectively representing over 70 million person-years of follow-up.

Among these, 733,776 patients, or 3.6% of the cohort, had a diagnosis of seborrheic dermatitis.

The study found that individuals with the condition were significantly more likely to have a broad range of epithelial barrier diseases (EBDs), from other dermatologic conditions such as rosacea, psoriasis, and alopecia areata, to extra-cutaneous disorders including coeliac disease, irritable bowel syndrome, dry eye and ocular allergy.

Using adjusted models, seborrheic dermatitis was positively associated with atopic dermatitis (odds ratio [OR], 3.21; 95% CI, 3.18-3.24); alopecia areata (OR, 4.02; 95% CI, 3.93-4.11); contact dermatitis (OR, 2.25; 95% CI, 2.23-2.26), psoriasis (OR, 3.26; 95% CI, 3.23-3.29); rosacea (OR, 4.52; 95% CI, 4.49-4.56); hidradenitis suppurativa (OR, 1.63; 95% CI, 1.58-1.68); chronic spontaneous urticaria (OR, 1.35; 95% CI, 1.33-1.37); pemphigus vulgaris (OR, 1.48; 95% CI, 1.31-1.69); bullous pemphigoid (OR, 1.60; 95% CI, 1.51-1.70); rhinosinusitis (OR, 1.24; 95% CI, 1.24-1.25); coeliac disease (OR, 1.36; 95% CI, 1.32-1.39); irritable bowel syndrome (OR, 1.32; 95% CI, 1.31-1.33); ocular allergy (OR, 1.39; 95% CI, 1.37-1.41); and dry eye (OR, 1.48; 95% CI, 1.48-1.49).

It was negatively associated with chronic obstructive pulmonary disease (OR, 0.72; 95% CI, 0.71-0.72) and pulmonary hypertension (OR, 0.70; 95% CI, 0.69-0.71).

“These findings support the EBT as a shared driver in the pathogenesis of seborrheic dermatitis and other diverse EBDs and encourage further investigation into the underlying mechanisms of disease pathogenesis,” the researchers wrote.

The results challenge the long-held perception of seborrheic dermatitis as an isolated skin problem. Instead, they portray it as part of a larger pattern of systemic vulnerability rooted in epithelial barrier breakdown – a process that may allow allergens, microbes, and pollutants to breach host defences, triggering inflammation not just in the skin but across organ systems.

This aligns closely with the epithelial barrier theory (EBT), which has emerged as a unifying model for a host of chronic inflammatory conditions spanning dermatology, gastroenterology and pulmonology.

The researchers say the study’s message is clear – SD may be a cutaneous marker of deeper epithelial instability. The same immune dysregulation and barrier compromise that drive erythema and scaling on the scalp or face may also predispose patients to inflammation in the gut or ocular surface.

The observed associations with disorders such as rosacea, alopecia areata and psoriasis underscored the extensive overlap among skin barrier diseases. Even after excluding or adjusting for potential diagnostic overlap with atopic dermatitis and psoriasis, the associations held steady, indicating that the findings cannot be dismissed as simple coding artifacts or misclassification errors.

Beyond the skin, seborrheic dermatitis was linked to gastrointestinal and ocular EBDs, including celiac disease (OR 1.36), irritable bowel syndrome (OR 1.32), ocular allergy (OR 1.39) and dry eye (OR 1.48).

The connection across such diverse epithelial surfaces suggests that barrier dysfunction may operate as a shared upstream process that amplifies systemic inflammation. This reinforces a growing body of evidence that epithelial health is a central determinant of chronic disease risk—and that loss of integrity in one tissue can reverberate throughout the body’s network of barrier sites.

The authors noted that the two conditions – COPD and pulmonary hypertension – that showed negative associations with seborrheic dermatitis was an unexpected finding. The said it may reflect differing cytokine dynamics or epithelial architecture in the lungs and vasculature.

“We believe that the negative associations between seborrheic dermatitis and COPD and pulmonary hypertension may be explained by differences in structure, physiology, and immunological mechanisms at different epithelial barriers,” they wrote.

“For example, EBT-mediated pathogenesis may be partially explained by damaged epithelial cells releasing inflammatory cytokines such as interleukin (IL)-1, IL-25, and IL-33, which leads to the influx and activation of immune cells.

“However, these cytokines have varying significance at different locations, with IL-25 being more prominent in gastrointestinal disorders, IL-33 in lung and gastrointestinal disorders, and IL-1 in a wide range of inflammatory disorders.

“Finally, factors other than epithelial disruption may contribute to disease, such as genetics, environmental factors, and alterations in the skin microbiome.”

The researchers note that while IL-1, IL-25 and IL-33 are implicated in the inflammatory cascade following epithelial injury, these cytokines exert tissue-specific effects that could explain why some barriers respond differently to the same systemic triggers.

While the study’s design cannot establish causality, its scale and rigour make it one of the most comprehensive examinations of the relationship between seborrheic dermatitis and systemic barrier dysfunction to date.

From a clinical standpoint, the implications are significant. Dermatologists may need to think beyond topical control of seborrheic dermatitis and consider the broader context of epithelial health, the researchers said.

The study suggests that patients presenting with chronic seborrheic dermatitis could be at higher risk for other barrier-related diseases and may benefit from screening or coordinated management across specialties.

For example, persistent seborrheic dermatitis accompanied by gastrointestinal symptoms might warrant evaluation for irritable bowel syndrome or coeliac disease; while coexisting ocular irritation could point toward dry eye or allergic conjunctivitis rooted in similar barrier disruption.

Despite the strengths of its enormous dataset, the researchers acknowledged some limitations. Claims-based data lack granularity on disease severity, laboratory markers and treatment history, and they exclude uninsured populations.

“The results both support and encourage further evaluation of the EBT model in the pathogenesis of EBDs,” they concluded.

“Future studies can be conducted to investigate the temporal relationship between seborrheic dermatitis and EBDs and to explore the underlying molecular mechanisms linking seborrheic dermatitis to EBDs, which will better characterise the role of the EBT model in disease pathogenesis.”

JAMA Dermatology, November 2025