Seborrheic dermatitis (SD) is a chronic, relapsing inflammatory dermatosis affecting sebaceous-rich areas (scalp, face, chest), characterized by erythematous plaques with greasy scale and pruritus of variable intensity. Multifactorial pathogenesis implicates host susceptibility, Malassezia yeast overgrowth, altered skin barrier and immune responses, and environmental factors. Management emphasizes antifungal therapy, anti-inflammatory agents during flares, keratolytics for scale, and maintenance regimens to reduce relapses.
Epidemiology
- Bimodal peaks: infancy (cradle cap) and adulthood, with prevalence ~3–10% in adults.
- More common in males and in those with oily skin.
- Increased prevalence/severity in HIV infection, Parkinson disease, and certain neurologic or psychiatric conditions.
Pathophysiology
- Malassezia species metabolize sebum, producing irritant metabolites that can trigger inflammation in predisposed hosts.
- Innate immune activation and barrier dysfunction contribute to chronicity.
- Sebum quantity and composition, climate (cold/dry), and stress modulate disease activity.
Clinical Features
- Scalp: diffuse greasy scale with or without erythema; dandruff is a mild, non-inflammatory variant.
- Face: eyebrows, glabella, nasolabial folds, beard area, retroauricular; pink plaques with yellowish, greasy scale.
- Trunk: presternal and interscapular patches/plaques; intertriginous involvement can macerate.
- Infants: thick adherent scalp scale; involves eyebrows, postauricular folds, neck, axillae, diaper area; generally non-pruritic.
- Pruritus ranges from mild to moderate; burning may be reported.
Differential Diagnosis
- Psoriasis (thicker, drier scale; well-demarcated; nail changes), tinea capitis (especially in children, consider KOH/culture), atopic dermatitis (more itch, flexural), rosacea (central face papulopustules without much scale), lupus (photo-distribution, dyspigmentation), HIV-related dermatoses in severe/refractory cases.
Diagnosis
- Clinical; no routine labs needed.
- Consider fungal studies (KOH) if tinea suspected; biopsy rarely required but shows spongiotic dermatitis with parakeratosis around follicular openings.
Management
- Antifungal therapy (first-line)
- Shampoos (2–3 times per week, then weekly maintenance):
- Ketoconazole 1–2%, ciclopirox 1%, selenium sulfide, zinc pyrithione, coal tar.
- Topical creams/gels for face and trunk:
- Ketoconazole 2% cream/gel, ciclopirox 1% cream, applied once or twice daily during flares, then 1–3 times weekly maintenance.
- Anti-inflammatory therapy (for flares)
- Low-potency topical corticosteroids for face/intertriginous areas (e.g., hydrocortisone 1% or 2.5%) for short courses (5–7 days).
- Mid-potency corticosteroids for scalp plaques (e.g., fluocinolone solution, clobetasol foam for limited, short-term use).
- Topical calcineurin inhibitors (tacrolimus/pimecrolimus) are steroid-sparing options for facial/intertriginous sites; effective for maintenance.
- Keratolytics and scale control
- Salicylic acid 3–6%, urea 10–20%, propylene glycol, coal tar; mineral oil/olive oil soaks in infants.
- Maintenance and prevention
- Intermittent antifungal shampoo and/or cream 1–3 times weekly.
- Reduce triggers: manage stress, avoid harsh detergents, consider climate humidification in winter.
- Special Populations
- Infants: emollients and gentle scale removal; ketoconazole 2% cream/shampoo short courses are safe; avoid high-potency steroids.
- HIV/Parkinson disease: often more severe—consider more frequent antifungal use and combination regimens.
Emerging and adjunctive therapies
- Foam and leave-on azole formulations, topical ivermectin or metronidazole for overlapping rosacea-like features, microbiome-directed care is under study.
References (recent guidelines and reviews)
- AAD/International guidance on dandruff and SD management, 2022–2024 updates.
- European expert consensus on antifungal and anti-inflammatory protocols for SD, 2023.
- Reviews on Malassezia-related dermatoses and SD pathophysiology, 2022–2024.