Seborrheic Dermatitis (Sebderm): Causes, Features & Treatment Overview

1. What is seborrheic dermatitis?

Seborrheic dermatitis is a chronic, relapsing inflammatory skin disease affecting sebaceous (oil-rich) areas:

• Scalp
• Face (especially eyebrows, nasolabial folds, glabella)
• Ears, presternal chest, upper back, body folds

It’s strongly associated with Malassezia (yeast), sebum, and abnormal immune response.

Prevalence: about 1–3% of the general population, much higher in HIV and neurologic disease (e.g. Parkinson’s).

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2. Pathophysiology (high-yield idea level)

Key components:(New England Journal of Medicine)

1. Malassezia overgrowth
   • Lipophilic yeast in sebaceous areas
   • Metabolizes sebum → free fatty acids → irritant + pro-inflammatory effect
2. Sebum & barrier dysfunction
   • SD occurs in sebum-rich areas; altered lipid composition and barrier function contribute.
3. Immune dysregulation
   • Exaggerated immune response to Malassezia in some people
   • Explains association with HIV and neurologic disorders.(Merck Manuals)

Think of SD as: “Malassezia + oily skin + abnormal immune reaction → chronic erythematous, greasy scaling.”

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3. Clinical features of seborrheic dermatitis

Adults

• Distribution (very important!)
  • Scalp: dandruff → diffuse, fine or coarse white/yellow greasy scales
  • Face: eyebrows, glabella, nasolabial folds, beard area
  • Ears: external ear canal, retroauricular folds (often fissuring behind ears)
  • Chest: ill-defined erythematous plaques with greasy scale over presternum
  • Body folds: axillae, groin, inframammary, umbilicus
• Morphology
  • Ill-defined erythematous patches/plaques
  • Greasy, yellowish scale
  • Mild–moderate pruritus (itch)

Infants (cradle cap)

• Age: first weeks–months of life
• Thick, greasy, yellow scales on scalp, sometimes involving face and folds
• Usually non-itchy, baby generally well
• Often resolves spontaneously in months

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4. How is seborrheic dermatitis different from psoriasis?

Psoriasis is a chronic immune-mediated disease with well-demarcated erythematous plaques and thick, dry, silvery scale, common on extensor surfaces (elbows, knees), scalp, sacrum, and associated with nail changes and arthritis.

Seborrheic dermatitis vs Psoriasis – exam comparison

There is an overlap called “sebopsoriasis” – psoriasis in seborrheic areas, with overlapping features.

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5. Other important differential diagnoses

From guidelines and reviews, frequent differentials include:(New England Journal of Medicine)

1. Atopic dermatitis (eczema)
   • Personal or family history of atopy
   • Flexural involvement, very pruritic, lichenification; onset usually childhood.
2. Tinea capitis / tinea corporis
   • Fungal infection; can mimic scalp SD or psoriasis.
   • Look for broken hairs, black dots, lymphadenopathy (especially in kids).
   • Confirm with KOH or fungal culture; tinea does not improve with typical SD treatment.
3. Contact dermatitis (allergic/irritant)
   • Well-demarcated in area of contact with cosmetic, shampoo, etc.; often more pruritic, vesicles possible.
4. Rosacea (face)
   • Central facial erythema, papules/pustules, telangiectasia, no significant scale.
5. Lupus erythematosus / secondary syphilis
   • Consider if systemic symptoms, photosensitivity, mucosal lesions, palmar/plantar rash, etc.

Key exam point:If the scalp looks “seborrheic,” but there is nail pitting or well-demarcated thick plaques on elbows/knees → think psoriasis first.

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6. Diagnosis

• Mostly clinical: based on typical distribution + greasy scale + chronic relapsing course.(AAFP)
• Dermoscopy: can help distinguish from psoriasis/tinea capitis in difficult scalp cases.(dermatologyadvisor.com)
• Biopsy: rarely needed; reserved for atypical cases or to rule out psoriasis, tinea, cutaneous lymphoma, etc.

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7. Management of seborrheic dermatitis

Principles:(AAFP)

1. Chronic disease → focus on control, not cure.
2. Combine anti-inflammatory + antifungal therapies.
3. Use low-potency steroids short-term; avoid chronic continuous use.
4. Maintenance: intermittent antifungal or medicated shampoo.

7.1 Scalp seborrheic dermatitis (dandruff to moderate SD)

First-line (mild–moderate): medicated shampoos

Use 2–3 times/week, leave on 5–10 minutes before rinsing; alternate agents if needed:

• Ketoconazole 2% shampoo – antifungal against Malassezia
• Ciclopirox 1% shampoo
• Zinc pyrithione, selenium sulfide, coal tar, salicylic acid shampoos

For exams, you can phrase:

Ketoconazole 2% shampoo, apply 2–3×/week to scalp, leave 5–10 minutes then rinse; continue for several weeks, then once weekly for maintenance.

If significant inflammation / itching:

• Add low- to mid-potency topical corticosteroid lotion/solution/foam: e.g. hydrocortisone 1%, betamethasone valerate 0.1% solution once–twice daily for 1–2 weeks, then taper.

Avoid: long-term daily steroids on scalp → atrophy, telangiectasia, tachyphylaxis.

7.2 Face and body (non-scalp) seborrheic dermatitis

1) Topical antifungals (mainstay)

• Ketoconazole 2% cream or ciclopirox 1% cream
• Apply once–twice daily to affected areas for 2–4 weeks; then intermittently for maintenance (e.g. 2–3×/week).(AAFP)

2) Low-potency topical corticosteroids (short courses)

• Hydrocortisone 1% cream bid for 5–7 days during flares, especially on face/folds.
• Avoid high-potency steroids on face → skin atrophy, telangiectasia, perioral dermatitis.

Evidence supports short courses of weak steroids + imidazole antifungal for non-scalp SD.(JDD Online)

3) Topical calcineurin inhibitors (TCIs)

• Tacrolimus 0.03–0.1% ointment or pimecrolimus 1% cream as steroid-sparing agents, particularly on face and intertriginous areas.(JDD Online)
• Good for long-term maintenance.
• Not first-line in some guidelines due to theoretical malignancy risk; use when steroids are contraindicated or for recurrent flares.

4) General skincare

• Gentle, non-soap cleansers; avoid harsh scrubs or strong alcohol-based products.
• Regular shampooing even with non-medicated shampoo helps reduce scale.

7.3 Severe, widespread, or refractory seborrheic dermatitis

Consider:(New England Journal of Medicine)

1. Screen for underlying conditions
   • HIV (especially if sudden, severe, or recalcitrant SD)
   • Neurologic disease (Parkinson’s)
2. Oral antifungals (short course)
   • Oral itraconazole, fluconazole, or terbinafine in selected, resistant cases under specialist guidance.
3. Newer non-steroidal options
   • PDE-4 inhibitors and “device” creams are emerging but more specialty-level/exam-advanced.(Dermatology Times)

7.4 Infantile seborrheic dermatitis (cradle cap)

Most cases are benign and self-limited.(DermNet®)

• First-line:
  • Emollient/oil (mineral oil, baby oil) to soften scale → gentle brushing/combing.
  • Mild baby shampoo.
• If persistent or inflamed:
  • Ketoconazole 2% shampoo/cream 2–3×/week for a few weeks.
  • Very short course of low-potency topical steroid (e.g. hydrocortisone 1% for a few days) if significant erythema/pruritus.

Avoid strong steroids, salicylic acid on infants, or aggressive manual removal.

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8. Quick exam pearls (especially vs psoriasis)

1. Distribution is king
   • SD = sebaceous: scalp, eyebrows, nasolabial folds, retroauricular, presternal, body folds.
   • Psoriasis = extensor plaques (elbows, knees), lumbosacral, scalp with thick plaques, nail pitting.
2. Type of scale
   • SD: thin, greasy, yellowish
   • Psoriasis: thick, dry, silvery, positive Auspitz sign.
3. Response to therapy
   • SD: improves with antifungal shampoos/creams ± mild steroids.
   • Psoriasis: responds better to stronger anti-inflammatory/immune-modulating therapy (e.g. vitamin D analogues, higher-potency steroids, biologics in severe disease).
4. Chronic and relapsing
   • Tell patients they will likely need intermittent maintenance (e.g. medicated shampoo once weekly).