What is the cause and treatment for seborrheic dermatitis?

Seborrheic Dermatitis: Cause and Treatment

Cause

Seborrheic dermatitis results from an inflammatory response to Malassezia yeast species that colonize sebum-rich areas of the skin. 1, 2 The pathophysiology involves Malassezia metabolizing sebum triglycerides into irritating free fatty acids that trigger inflammation, combined with immune dysregulation and skin barrier dysfunction. 2, 3

• The condition affects areas with high sebaceous gland density: scalp, face (especially nasolabial folds, eyebrows, retroauricular areas), central chest, back, and body folds. 4, 3
• Malassezia ovale (Pityrosporum ovale) is the primary organism implicated, though the exact mechanism remains incompletely understood. 5, 6
• The disease is more pronounced in patients with HIV infection, Parkinson's disease, and Down syndrome. 2

Treatment Approach

The most effective treatment combines topical antifungal medications to reduce Malassezia yeast with topical anti-inflammatory agents to control inflammation and itching. 1

First-Line Therapy: Topical Antifungals

Topical ketoconazole is the mainstay of therapy for seborrheic dermatitis of the face and body. 5, 4

• For facial and body involvement: Apply ketoconazole 2% cream twice daily for four weeks or until clinical clearing. 5
• For scalp involvement: Use antifungal shampoos as first-line therapy, with ketoconazole being highly effective. 4, 6
• Ketoconazole works by impairing ergosterol synthesis in fungal cell membranes and reducing Malassezia colonization. 5
• Other effective topical antifungals include ciclopirox, terbinafine, and bifonazole. 6

Second-Line Therapy: Anti-Inflammatory Agents

Low-potency topical corticosteroids should be used only for short-term control of inflammation and itching. 1, 2

• Use the least potent preparation required to control symptoms. 1
• Critical caveat: Avoid long-term use of topical corticosteroids, especially on the face, due to risk of skin atrophy, telangiectasia, and tachyphylaxis. 1, 2
• Topical calcineurin inhibitors (tacrolimus, pimecrolimus) can be used as steroid-sparing alternatives for short-term use. 4, 3

Supportive Care

Gentle skin care with mild, non-soap cleansers and emollients helps reduce dryness and scaling. 1, 2

• Use dispersible creams as soap substitutes, as soaps remove natural lipids from the skin surface. 1
• Apply emollients after bathing to provide a surface lipid film that retards evaporative water loss. 1
• For facial seborrheic dermatitis: Avoid alcohol-containing preparations as they increase skin dryness. 1, 2
• Use non-greasy moisturizers with urea or glycerin applied after bathing. 1

Adjunctive Therapy

• For moderate to severe pruritus: Oral antihistamines (cetirizine, loratadine, fexofenadina) can provide symptomatic relief. 1
• Antihistamines with sedative properties are useful as short-term adjuvants during severe flares with intense pruritus. 1
• For scalp involvement: Coal tar preparations can reduce inflammation and scaling. 1

Systemic Therapy for Severe or Resistant Cases

Oral antifungals are reserved for widespread or treatment-resistant seborrheic dermatitis. 6, 7

• Itraconazole: 200 mg/day for the first week of the month, then 200 mg/day for the first 2 days monthly for 2-11 months. 7
• Terbinafine: 250 mg/day either continuously for 4-6 weeks or intermittently (12 days per month) for 3 months. 7
• Fluconazole: 50 mg/day for 2 weeks or 200-300 mg weekly for 2-4 weeks. 7
• Ketoconazole oral therapy is associated with more relapses compared to other systemic antifungals. 7

Treatment Duration and Maintenance

Treatment should be continued for the full prescribed duration even if symptoms improve sooner. 2

• Facial and body lesions typically require 2-4 weeks of treatment. 5
• Due to the chronic, relapsing nature of seborrheic dermatitis, maintenance therapy with emollients and intermittent anti-inflammatory treatment may be necessary. 2
• Long-term antifungal shampoos can be used for maintenance of scalp involvement. 4

Common Pitfalls to Avoid

• Do not use neomycin in topical preparations due to risk of sensitization. 1
• Distinguish seborrheic dermatitis from psoriasis, atopic dermatitis, and contact dermatitis, which require different treatment approaches. 1, 2
• Avoid undertreatment due to fear of steroid side effects, but equally avoid overuse of corticosteroids. 1
• Treat secondary bacterial infection with appropriate antibiotics if present (look for crusting, weeping, or purulent exudate). 1
• Non-sedating antihistamines have little value in seborrheic dermatitis and should not be overused. 1