What is seborrheic dermatitis?

Seborrheic Dermatitis: Definition, Pathophysiology, and Management

Seborrheic dermatitis is a common chronic inflammatory skin condition characterized by greasy yellowish scaling, erythema, and inflammation that primarily affects areas rich in sebaceous glands, with pathogenesis involving Malassezia yeast proliferation, sebum production, and immune dysregulation. 1

Clinical Presentation

• Presents as symmetric, poorly defined erythematous patches with yellow, oily scales and fine, superficial desquamation (flaking) in sebaceous gland-rich areas 2
• Commonly affects the scalp, face (particularly around the eyebrows, nasolabial folds, and ears), central anterior trunk, and body folds 3
• In individuals with darker skin tones, erythema may be less apparent, with hypopigmented, slightly scaly areas being more prominent 2
• Scalp involvement may be misdiagnosed as dandruff or simple scaling 4
• Often associated with pruritus, which can significantly impact quality of life 1

Pathophysiology

• Three key factors contribute to seborrheic dermatitis development:
  • Increased lipid secretion by sebaceous glands 1
  • Malassezia yeast colonization and proliferation 1
  • Immunologic dysregulation that predisposes to inflammatory response 1
• The condition involves skin barrier dysfunction, microbial dysbiosis, and immune imbalance 3
• Malassezia species metabolize sebum triglycerides, producing irritating free fatty acids that trigger inflammation 5

Associated Conditions

• More pronounced in patients with:
  • HIV infection 6
  • Parkinson's disease 6
  • Down syndrome 6
• Seborrheic dermatitis is frequently associated with seborrheic dermatitis of the skin, with 95% of patients with seborrheic blepharitis also having seborrheic dermatitis 4
• May co-occur with dry eye conditions in 25-40% of cases 4

Treatment Approaches

First-Line Treatments

• Topical antifungal medications to reduce Malassezia yeast colonization:

  • Ketoconazole cream 2% applied to affected areas twice daily for four weeks is FDA-approved for seborrheic dermatitis 7
  • If no clinical improvement occurs after the treatment period, the diagnosis should be reconsidered 7

• Topical anti-inflammatory agents to control inflammation and itching:

  • Low-potency topical corticosteroids for short-term use 5
  • Calcineurin inhibitors as steroid-sparing alternatives 8
  • Caution: Avoid long-term use of topical corticosteroids, especially on the face, due to risk of skin atrophy, telangiectasia, and tachyphylaxis 5

Adjunctive Measures

• Gentle skin care with mild, non-soap cleansers to reduce dryness and scaling 5
• Emollients applied after bathing to provide a surface lipid film that retards evaporative water loss 5
• For scalp involvement:
  • Antifungal shampoos containing ketoconazole, selenium sulfide, or zinc pyrithione 2
  • Keratolytic shampoos containing salicylic acid or coal tar for thick, scaly areas 2

For Resistant Cases

• Topical phosphodiesterase-4 inhibitors (roflumilast 0.3% foam) show promise as a newer non-corticosteroid option 3
• Systemic therapy is reserved only for widespread lesions or cases refractory to topical treatment 9

Special Considerations

• Neonatal seborrheic dermatitis (cradle cap) typically self-resolves by 6 months of age; mild cases can be treated with mineral oil to loosen scale and gentle combing 2
• Avoid alcohol-containing preparations on facial seborrheic dermatitis as they may increase skin dryness 5
• Distinguish from similar conditions like psoriasis, atopic dermatitis, and contact dermatitis, which require different treatment approaches 5

Treatment Duration and Maintenance

• Continue treatment for the full prescribed duration even if symptoms improve sooner 6
• Due to the chronic, relapsing nature of seborrheic dermatitis, maintenance therapy with emollients and intermittent anti-inflammatory treatment may be necessary 6
• Regular use of antifungal products may help prevent recurrence 9