What is the differential diagnosis and treatment for a red flaky rash on the face and scalp?

Differential Diagnosis for Red Flaky Rash on Face and Scalp

Seborrheic dermatitis is the most likely diagnosis for a red flaky rash affecting both the face and scalp, characterized by greasy yellowish scaling with erythema in sebaceous-rich areas. 1, 2

Primary Differential Diagnoses

Seborrheic Dermatitis (Most Common)

• Presents with greasy yellowish scaling, erythema, and itching primarily in sebaceous areas including scalp, face (especially nasolabial folds, eyebrows, and retroauricular areas) 1, 2
• Associated with Malassezia yeast overgrowth 2, 3
• May show hyperpigmentation or hypopigmentation in darker skin types, with minimal or absent erythema and scaling 3
• More common in patients with Parkinson's disease, HIV/AIDS, or Down syndrome 1, 4

Psoriasis

• Characterized by well-demarcated, red plaques with silvery-white scale, commonly involving scalp, face, elbows, and knees 5, 6
• Sharply demarcated borders distinguish it from seborrheic dermatitis 6
• Scalp involvement shows thick, adherent scaling 6
• Less "greasy" appearance compared to seborrheic dermatitis 5

Atopic Dermatitis

• Presents with eczematous changes including oozing and crusting 5
• More pruritic than seborrheic dermatitis 5
• Typically affects flexural areas in adults, though face and scalp can be involved 5
• Associated with personal or family history of atopy 5

Contact Dermatitis (Allergic or Irritant)

• Shows atypical or localized distribution patterns 5
• History of new products, cosmetics, or hair care products is key 5
• Patch testing may be indicated if suspected 5

Tinea Capitis/Faciei

• Annular papulosquamous lesions without eczematous change 5
• Requires skin scraping for microscopy and fungal culture for confirmation 5
• More common in children but can occur in adults 5

Rosacea (Face Only)

• Presents with central facial erythema, papules, pustules, and telangiectasias 5
• Does not typically involve scalp 5
• Flushing episodes are characteristic 5

Treatment Approach

For Seborrheic Dermatitis (First-Line)

Scalp Treatment:

• Ketoconazole 2% shampoo applied twice weekly as primary antifungal therapy 7, 2
• Alternative antifungal shampoos include selenium sulfide, zinc pyrithione, or ciclopirox 2, 8
• For severe scalp involvement: clobetasol propionate 0.05% shampoo for short-term use only (2-4 weeks maximum) to avoid adverse effects 1, 2
• Coal tar shampoos (2-10% coal tar solution) as alternative therapy 1, 6

Facial Treatment:

• Ketoconazole 2% cream applied once daily to affected areas for 2-4 weeks 7, 2
• Low-potency topical corticosteroids (hydrocortisone 1-2.5%) for short-term use only (maximum 2-3 weeks) due to risk of skin atrophy on face 5, 2
• Topical calcineurin inhibitors (tacrolimus, pimecrolimus) as steroid-sparing alternatives for facial involvement 2

Maintenance Therapy:

• Continue antifungal therapy long-term (ketoconazole 2% cream 1-2 times weekly) to prevent recurrence 2, 8
• Emollients applied twice daily to maintain skin barrier 1

For Psoriasis

Scalp Treatment:

• Calcipotriol (vitamin D3 analog) solution for scalp, which inhibits epidermal proliferation and inflammation 6
• High-potency topical corticosteroids (clobetasol 0.05% or fluocinonide 0.05%) as solution for scalp 5, 6
• Salicylic acid 5-10% in ointment base for keratolytic effect to remove thick scale 6
• Coal tar preparations (crude coal tar most effective) 6

Facial Treatment:

• Low-to-medium potency corticosteroids for face (avoid high-potency on face) 5
• Vitamin D3 analogs (calcipotriol) for face 5, 6
• Tacrolimus 0.1% ointment as steroid-sparing option 5

For Atopic Dermatitis

• Medium-to-high potency topical corticosteroids for 1-4 weeks for clearance, followed by proactive maintenance therapy 2-3 times weekly 5
• Topical calcineurin inhibitors for maintenance and steroid-sparing 5
• Intensive emollient therapy (200-400g per week for face, scalp, and affected areas) 5

Critical Diagnostic Pitfalls

Common Mistakes to Avoid:

• Do not use high-potency corticosteroids on the face long-term—this causes skin atrophy, telangiectasia, and perioral dermatitis 5, 1
• Seborrheic dermatitis in darker skin may present with minimal erythema and scaling, showing primarily pigmentary changes 3
• Overuse of topical corticosteroids on scalp can lead to systemic absorption and adverse effects 1
• Contact dermatitis from hair care products or topical treatments can mimic or complicate primary dermatoses 5
• Bacterial superinfection (especially Staphylococcus aureus) should be suspected if there is failure to respond to standard therapy, presence of yellow crusts, or painful lesions 5

When to Escalate Care

• Refer to dermatology if no improvement after 4 weeks of appropriate first-line therapy 1, 8
• Consider skin biopsy if diagnosis remains uncertain after initial treatment trial 5
• Fungal culture and microscopy if tinea is suspected 5
• Patch testing if allergic contact dermatitis is suspected 5