What is the treatment for a patient presenting with an itchy scalp?

Treatment of Itchy Scalp

For an itchy scalp, begin with an antifungal shampoo containing ketoconazole, selenium sulfide, or pyrithione zinc as first-line therapy, since the most common cause is seborrheic dermatitis driven by Malassezia yeast. 1, 2

Initial Diagnostic Considerations

Before treating, identify the underlying cause by examining for:

• Seborrheic dermatitis: Greasy or powdery scale along hair margins, often with facial involvement 1, 2
• Scalp psoriasis: Thick, adherent silvery scale with well-demarcated plaques 3
• Head lice: Visible nits attached to hair shafts, particularly behind ears and at nape of neck 4
• Atopic dermatitis: History of eczema elsewhere, dry scaling without greasiness 4, 5

First-Line Treatment Algorithm

For Seborrheic Dermatitis (Most Common)

Start with over-the-counter antifungal shampoos containing one of these active ingredients 1, 2:

• Ketoconazole 1-2% shampoo (apply twice weekly, leave on 3-5 minutes before rinsing) 1, 2
• Selenium sulfide shampoo 2, 6
• Pyrithione zinc shampoo 2, 6

If over-the-counter shampoos fail after 2-4 weeks, escalate to 1:

• Prescription ketoconazole 2% cream applied to affected scalp areas once daily for 2-4 weeks 7, 1
• Short-term topical corticosteroids (see below) 1, 2

For Scalp Psoriasis

Use topical corticosteroids as the mainstay, since effects are rapid (2-3 weeks vs. 8 weeks for vitamin D analogues) 3:

• Clobetasol propionate 0.05% shampoo applied once daily for up to 4 consecutive weeks 8
• Apply to dry scalp, lather, leave on for 15 minutes, then rinse 8

Add keratolytic agents for thick scale 3:

• Salicylic acid preparations applied overnight under occlusion to soften plaques 3, 6

Alternate or combine with vitamin D3 analogues (calcipotriol lotion) for maintenance after initial corticosteroid response 3

For Atopic Dermatitis of Scalp

Apply topical corticosteroids to affected areas 4, 5:

• Use moderate-to-potent corticosteroids (the scalp tolerates higher potencies due to thicker skin) 4, 5
• Apply no more than twice daily 5
• Consider coal tar preparations when scalp is primarily involved 4

Maintain with aggressive emollient use even when controlled 5, 9

Managing the Itch Itself

Topical corticosteroids directly address inflammation-driven pruritus 4, 10:

• Hydrocortisone 1-2.5% for mild itching (apply 3-4 times daily) 10
• Higher potency corticosteroids for moderate-to-severe pruritus 4, 5

For nighttime itch disrupting sleep, prescribe sedating antihistamines 5, 9:

• Diphenhydramine or hydroxyzine at bedtime only 5, 9
• The benefit comes from sedation, not direct anti-pruritic effects 5, 9
• Do not use non-sedating antihistamines—they have no value in scalp dermatitis 5, 9

Persistent itching after treatment may represent 4:

• Inflammatory response to the topical agent itself (not a reason for re-treatment) 4
• Consider topical corticosteroids or oral antihistamines for post-treatment pruritus 4

Critical Pitfalls to Avoid

Do not undertreat with corticosteroids due to "steroid phobia"—the scalp tolerates potent preparations better than facial or flexural areas 4, 3

Do not use continuous corticosteroid therapy beyond 4 weeks without breaks, as safety data for prolonged use are lacking 3

Do not assume all itchy scalp is "just dandruff"—examine carefully for 4:

• Head lice (treat with permethrin 1% or malathion 0.5% if present) 4
• Secondary bacterial infection (increased crusting, weeping, pustules requiring oral flucloxacillin) 5, 9
• Fungal infection with dermatophytes (consider if increased itching in ichthyotic or immunocompromised patients) 4

Watch for Malassezia fungal overgrowth in patients with recurrent symptoms—this lipophilic yeast drives both dandruff and seborrheic dermatitis 1, 2, 6

When to Refer

• Failure to respond to appropriate first-line therapy after 4 weeks 5
• Severe, widespread scalp involvement requiring systemic therapy 4
• Diagnostic uncertainty between psoriasis, seborrheic dermatitis, and other conditions 1