What is causing my itchy, greasy, and irritated scalp, which is relieved by daily shampooing and application of mometasone (mometasone) lotion, given my history of eczema (atopic dermatitis)?

Scalp Seborrheic Dermatitis with Secondary Atopic Component

You most likely have seborrheic dermatitis of the scalp, which is characterized by the exact symptoms you describe—greasy, clumpy buildup with intense itching that responds dramatically to daily shampooing and topical corticosteroids like mometasone. 1

What's Happening on Your Scalp

Your symptoms fit the classic presentation of seborrheic dermatitis rather than typical atopic dermatitis:

• Greasy, clumpy texture: Seborrheic dermatitis produces yellowish, greasy scaling that accumulates rapidly, unlike the dry scaling of pure atopic eczema 1, 2
• Daily buildup requiring washing: The Malassezia yeast that drives seborrheic dermatitis produces oils and inflammatory byproducts that accumulate within 24 hours, explaining why skipping even one day causes severe symptoms 1
• Immediate relief from shampooing: Mechanical removal of the greasy scales and yeast provides rapid symptom relief 3
• Dramatic response to mometasone: Topical corticosteroids are first-line treatment for scalp dermatitis and address the inflammation directly 1, 4

Why This Happens in People with Eczema

Patients with atopic dermatitis have compromised skin barrier function, making them more susceptible to developing seborrheic dermatitis as a secondary condition. 5

• Your underlying atopic tendency creates a disrupted epidermal barrier that allows Malassezia yeast overgrowth 5
• The combination of atopic dermatitis and seborrheic dermatitis on the scalp is well-documented, with significant overlap between these conditions 2, 3

Optimal Management Strategy

Daily Maintenance (What You're Already Doing Right)

Continue daily shampooing—this is medically appropriate and necessary for seborrheic dermatitis, not excessive. 1, 3

• Use a gentle, soap-free cleanser or medicated shampoo rather than harsh detergents 6
• Consider antifungal shampoos containing ketoconazole 2%, which target the Malassezia yeast driving your symptoms 4, 3
• Apply mometasone lotion to affected areas once daily after shampooing when symptomatic 7

Specific Treatment Protocol

For active flares (like what you experienced last night):

• Apply mometasone 0.1% lotion once daily to the scalp, massaging until it disappears 7
• The lotion formulation is specifically designed for scalp application and penetrates hair-bearing areas effectively 7
• Continue treatment for at least 7 days even after symptoms improve 1

For maintenance between flares:

• Daily shampooing with antifungal shampoo (ketoconazole 2% used 2-3 times weekly) 4, 3
• Intermittent mometasone application (1-2 times weekly) may prevent recurrence 8
• Keep the scalp dry and avoid occlusive head coverings 1

Important Caveats and Pitfalls

Don't Reduce Washing Frequency

The common advice to "wash less often" does not apply to seborrheic dermatitis—daily washing is therapeutic, not harmful. 1, 3

• Seborrheic dermatitis produces rapid accumulation of greasy scales and inflammatory mediators 2
• Skipping washing allows yeast proliferation and symptom escalation 1

Monitor for Corticosteroid Side Effects

While mometasone is relatively safe, prolonged daily use carries risks:

• Watch for scalp thinning, telangiectasia (visible blood vessels), or shininess 7
• If using daily for more than 2 weeks without improvement, reassess the diagnosis 7
• Consider transitioning to twice-weekly maintenance dosing once controlled 8

Avoid These Common Mistakes

• Don't use neomycin-containing products: These cause allergic reactions in 5-15% of patients with chronic skin conditions 1
• Don't scratch: This creates a self-perpetuating itch-scratch cycle and can cause secondary bacterial infection 5
• Don't use occlusive coverings: These worsen seborrheic dermatitis by trapping moisture and promoting yeast growth 1, 7

When to Seek Further Evaluation

Consider dermatology referral if:

• No improvement after 2 weeks of appropriate treatment 7
• Signs of secondary bacterial infection develop (crusting, weeping, honey-colored discharge) 6
• Extensive involvement beyond the scalp 6
• Severe impact on quality of life despite treatment 6

Your current approach of daily shampooing plus mometasone for flares is medically sound and should be continued. Adding an antifungal shampoo would likely provide additional benefit by targeting the underlying Malassezia yeast component. 4, 3