Seborrheic dermatitis
Seborrheic dermatitis is a common chronic inflammatory reaction to Malassezia yeast that produces ill-defined erythema with dry or greasy scale in sebum-rich sites such as the scalp, nasolabial folds, brows, and ears. Diagnosis is clinical based on distribution; first-line treatment is topical ketoconazole cream or shampoo with a short course of low-potency hydrocortisone for inflamed flares, and disseminated or severe disease should prompt screening for HIV or a neurologic disorder.
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What this article covers
- Overview
Definition: seborrheic dermatitis is a common, chronic inflammatory skin disease that develops in areas rich in sebaceous glands, driven by an inflammatory reaction to the yeast Malassezia furfur rather than a primary infection.
- Epidemiology
Age distribution: seborrheic dermatitis occurs in infants (cradle cap, with or without diaper rash) and separately in children and adults, where it produces red, scaly, thin plaques on the face, mid-chest, and scalp.
- Risk factors
HIV infection: patients with HIV/AIDS can develop severe, widespread seborrheic dermatitis, making a sudden florid presentation a reason to screen for HIV.
- Pathophysiology
Malassezia-driven inflammation: seborrheic dermatitis is an inflammatory response to Malassezia yeast, a generally harmless organism found in sebum and hair follicles, rather than a direct infection.
- Clinical features
Diagnostic pattern: ill-defined erythema with dry or greasy scale, distributed across the scalp (dandruff), nasolabial folds, cheeks, eyebrows, eyelids, external auditory canals, post-auricular skin, and central chest.
- Differential diagnosis
Rosacea: central-face erythema and papulopustules with flushing triggers and no comedones, distinguished by the absence of the greasy scale that defines seborrheic dermatitis.
- Diagnosis
Diagnostic basis: seborrheic dermatitis is a clinical diagnosis established by recognizing ill-defined erythema with dry or greasy scale confined to sebum-rich sites (scalp, nasolabial folds, brows…
- Management
First step, for facial or body involvement: apply ketoconazole 2% (20 mg/g) cream topically to the affected area twice daily for 4 weeks or until clinical clearing.
- Complications
Secondary infection: excoriated or chronically inflamed areas can become secondarily infected, particularly with repeated scratching of pruritic scalp or facial lesions.
- Prognosis
Chronic, relapsing course: seborrheic dermatitis is not curable but is well controlled with topical antifungal and anti-inflammatory therapy; recurrence after stopping treatment is expected.
- Prevention
Intermittent maintenance antifungal therapy: using ketoconazole shampoo or cream on a scheduled, intermittent basis (for example, continuing periodic use after the initial 4-week clearing course) reduces the frequency of relapse.
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Rosacea is a chronic inflammatory facial skin disorder with recurrent flushing that produces persistent central-face erythema, telangiectasias, and papulopustules without comedones, triggered by heat, sun, alcohol, and spicy food. Diagnosis is clinical based on subtype; treatment is matched to subtype, with topical metronidazole, azelaic acid, or ivermectin and oral doxycycline for papulopustular disease, laser therapy for telangiectasias, and laser or surgery for rhinophyma.
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Atopic dermatitis is a chronic, pruritic, relapsing inflammatory skin disease of the face and flexural surfaces driven by a compromised skin barrier and an exaggerated immune response, often accompanying allergic rhinitis and asthma as part of the atopic triad. First-line treatment is fragrance-free emollients plus a topical glucocorticoid for active flares, escalating to topical calcineurin inhibitors, phototherapy, or systemic agents such as dupilumab for disease recalcitrant to topical therapy.
- Tinea versicolor
Tinea versicolor (pityriasis versicolor) is a common superficial fungal infection caused by Malassezia yeast, producing hypopigmented, hyperpigmented, or erythematous scaly macules that coalesce into patches on the upper trunk and fail to tan with sun exposure. Diagnosis is confirmed by a potassium hydroxide preparation showing a spaghetti-and-meatballs pattern, and first-line treatment is topical ketoconazole 2% shampoo or selenium sulfide 2.5% lotion, with oral itraconazole reserved for extensive or recurrent disease.