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Seborrheic Dermatitis (SD)

Basics

  • Chronic, superficial, recurrent inflammatory skin disease.
  • Predominantly affects sebum-rich, hairy regions: scalp, eyebrows, face; less commonly chest and back.
  • Infants commonly present with cradle cap.
  • Occurs mostly in adolescence, infancy, and adulthood.
  • Male predominance.

Epidemiology

  • Global prevalence: 2-5%, up to 83% in HIV-positive/immunosuppressed.
  • Infantile SD common in first 3 months across ethnicities.

Etiology and Pathophysiology

  • Malassezia yeast colonization implicated.
  • Genetic and environmental triggers; flares with stress/illness.
  • Increased sebaceous activity during infancy/adolescence or with acnegenic drugs.
  • Immunosuppression increases incidence; immune mechanisms suspected but not well-defined.
  • Positive family history common; no specific genetic markers identified.

Risk Factors

  • Immunosuppression (HIV/AIDS).
  • Parkinson disease, neurologic disorders, facial paralysis.
  • Emotional stress.
  • Obesity, oily skin, acne.
  • Down syndrome.
  • Medications: buspirone, chlorpromazine, cimetidine, ethionamide, griseofulvin, haloperidol, interferon-Ξ±, methyldopa, psoralen, IL-2.

General Prevention

  • Frequent washing of seborrheic skin to soften scales.

Commonly Associated Conditions

  • Parkinson disease.
  • HIV/AIDS.
  • Facial paralysis.
  • Down syndrome.

Diagnosis

History

  • Intermittent phases with burning, scaling, itching.
  • Worse in winter/early spring; remits in summer.
  • Infantile "cradle cap": greasy scalp scaling, possible erythema.
  • Adults: red, greasy, scaling macules/plaques with indistinct margins.
  • Minimal pruritus.
  • Bilateral symmetric involvement of scalp, eyebrows, eyelids, nasolabial folds, ears, retroauricular folds, chest, back, genital and axillary areas.

Physical Exam

  • Scalp: mild patchy scaling to thick adherent crusts; plaques rare.
  • Lesions: brawny/yellow greasy scaling over red inflamed skin.
  • Hypopigmentation in darker skin tones.
  • Secondary infection presents with oozing/crusting.
  • Seborrheic blepharitis may occur.

Differential Diagnosis

  • Atopic dermatitis (harder to differentiate in infants).
  • Psoriasis: sharply demarcated plaques, nail involvement.
  • Candida infections.
  • Tinea (cruris/capitis).
  • Eczema of auricle/otitis externa.
  • Rosacea.
  • Discoid lupus erythematosus.
  • Histiocytosis X.
  • Dandruff (noninflammatory scalp only).
  • Drug eruption.

Diagnostic Tests

  • Skin biopsy if unclear or treatment failure.
  • Fungal cultures if refractory, pustules, or alopecia.
  • Histopathology: hyperkeratosis, acanthosis, spongiosis, parakeratosis around follicles, mild lymphocytic inflammation.

Treatment

General Measures

  • Increase shampoo frequency.
  • Moderate sunlight exposure may help.
  • Infantile: mild nonmedicated shampoos; mineral oil to remove thick scales.
  • Adults: antiseborrheic shampoos (selenium sulfide, coal tar, sulfur, salicylic acid).
  • For dense scaling: coal tar detergents (e.g., 10% liquor carbonis detergens) overnight under shower cap.

Medications

  • First Line:
  • Antifungal shampoos: ketoconazole 2%, miconazole 2%, ciclopirox 1% twice weekly.
  • Topical corticosteroids: hydrocortisone 1%, advance to fluorinated steroids short-term.
  • Topical antifungal creams: ketoconazole 2%, sertaconazole 2%.
  • Coal tar, selenium sulfide, zinc pyrithione shampoos twice weekly.

  • Lithium gluconate/succinate ointment/gel 8% twice weekly.

  • Precautions:

  • Avoid long-term potent steroids to prevent atrophy, hypopigmentation, systemic absorption.

  • Fluorinated steroids risky around eyes.

  • Second Line:

  • Calcineurin inhibitors (pimecrolimus 1% cream, tacrolimus 0.1% ointment).

  • Systemic antifungals for severe/recalcitrant cases (terbinafine, itraconazole).

  • Other Agents:

  • Low-molecular-weight hyaluronic acid gel for skin hydration.

Issues for Referral

  • Poor response to treatment.
  • Suspected systemic illness (HIV).

Complementary & Alternative Medicine

  • Honey, aloe vera, borage oil, tea tree oil, quassia amara extract show antifungal/anti-inflammatory effects.

Ongoing Care

  • Hair care varies by hair type; apply treatments directly to scalp to minimize hair damage.

Follow-Up Recommendations

  • Monitor every 2–12 weeks based on severity and response.

Patient Education

  • Refer to reliable sources like familydoctor.org for disease information.

Prognosis

  • Infantile SD usually resolves by 6–8 months.
  • Adult SD is chronic with remissions and exacerbations.
  • Erythema and hypopigmentation resolve with treatment.

Complications

  • Skin atrophy, striae from steroids.
  • Glaucoma/cataracts from periocular steroids.
  • Rare herpes keratitis; stop eyelid steroids if herpes simplex occurs.

ICD10 Codes:
- L21.9 Seborrheic dermatitis, unspecified
- L21.1 Seborrheic infantile dermatitis
- L21.0 Seborrhea capitis

Clinical Pearls:
- Consider systemic disease in refractory SD.
- Infantile SD is self-limited.
- Adult SD usually manageable with shampoos and topical steroids.
- Avoid prolonged potent steroid use, especially on face and folds.