What is the cause and treatment of seborrheic dermatitis?

Seborrheic Dermatitis: Causes and Treatment

Seborrheic dermatitis is primarily caused by an inflammatory response to Malassezia yeast, with contributing factors including sebaceous gland activity and immune dysregulation, and is most effectively treated with topical antifungal agents such as ketoconazole cream or shampoo applied daily for four weeks. 1, 2, 3

Pathophysiology and Causes

Seborrheic dermatitis is a chronic inflammatory skin condition characterized by:

• Primary pathogenic factor: Malassezia yeast (formerly known as Pityrosporum) proliferation 1, 3
• Contributing factors:
  • Sebaceous gland hyperactivity
  • Immune system dysregulation
  • Enhanced cell-mediated immunity to Malassezia (detected in 40% of chronic cases) 1

The condition typically affects sebum-rich areas of the body:

• Scalp
• Face (particularly nasolabial folds)
• Ears
• Chest
• Upper back
• Body folds (axillary, inframammary, inguinal) 1

Risk Factors

Seborrheic dermatitis is more pronounced in patients with:

• HIV infection
• Parkinson's disease
• Down syndrome 1
• Patients with seborrheic blepharitis (95% co-occurrence rate) 1

Clinical Presentation

The condition presents with:

• Follicular papules and pustules
• Greasy yellowish scaling
• Underlying erythema
• Pruritus and discomfort 1
• In darker skin, erythema may be less apparent with hypopigmented, scaly areas 4

Treatment Approach

First-Line Treatments

1. Topical Antifungal Agents (primary treatment):

   • Ketoconazole 2% cream or shampoo:
     • For face/body: Apply cream once daily for four weeks 2
     • For scalp: Use shampoo 2-3 times weekly 1, 3
   • Other options: ciclopirox, bifonazole, selenium sulfide 1, 5

2. Anti-inflammatory Agents (short-term use only):

   • Low-potency topical corticosteroids
   • Topical calcineurin inhibitors (tacrolimus, pimecrolimus) 1, 3

Location-Specific Treatment

Scalp Treatment:

• Begin with antifungal shampoo containing ketoconazole, selenium sulfide, or pyrithione zinc
• For thick scales: Add keratolytic shampoos 4
• For resistant cases: Short-term topical corticosteroid solutions/foams 3

Face and Body Treatment:

• Ketoconazole 2% cream applied once daily 2
• For inflammatory lesions: Short-term low-potency corticosteroids or calcineurin inhibitors 1, 3

Maintenance Therapy

After initial control (typically 4 weeks):

• Transition to maintenance with antifungal shampoo 1-2 times weekly
• Avoid greasy hair products that facilitate yeast growth
• Consider rotating between different antifungal agents to prevent resistance 1

Treatment for Resistant Cases

For moderate-to-severe or recalcitrant cases:

• Oral antifungals (ketoconazole, itraconazole, terbinafine) may be considered 5
• Newer options like roflumilast foam show promise as potential first-line treatments 6

Common Pitfalls to Avoid

1. Inadequate treatment duration: Complete the full recommended course (4 weeks for ketoconazole cream) 1

2. Misdiagnosis: Several conditions mimic seborrheic dermatitis:

   • Psoriasis
   • Atopic dermatitis
   • Tinea capitis
   • Contact dermatitis
   • Discoid lupus erythematosus 1

3. Prolonged use of potent corticosteroids: Can potentially worsen hair loss over time 1

4. Failure to implement maintenance therapy: Seborrheic dermatitis is chronic and relapsing, requiring ongoing management 1

5. Using greasy topical products: Can inhibit absorption of wound exudate and promote superinfection 1

Prevention Strategies

• Regular use of antifungal products
• Gentle cleansing with pH-neutral formulations
• Avoiding irritants and potential allergens
• Keeping affected areas dry
• Applying hypoallergenic moisturizing creams once daily 1

By understanding the pathogenesis of seborrheic dermatitis and following appropriate treatment protocols, most patients can achieve good control of this chronic, relapsing condition.