What is Seborrheic Dermatitis and Dandruff?
Seborrheic dermatitis and dandruff represent a continuous spectrum of the same inflammatory skin disease affecting sebaceous-rich areas of the body, with dandruff being the mildest form restricted to the scalp without visible inflammation, while seborrheic dermatitis involves visible inflammation, erythema, and greasy scaling that can affect the scalp, face, chest, and other seborrheic areas. 1
Core Pathophysiology
The disease mechanism centers on an inflammatory response to Malassezia yeast species, which colonize sebaceous-rich skin areas and metabolize sebum triglycerides into irritating free fatty acids that trigger localized inflammation 2, 3, 4. This is not a systemic or gut-related condition but rather a localized skin microbiome alteration with decreased fungal diversity and increased Malassezia counts 3.
Clinical Presentation
Dandruff (Mildest Form)
- Scalp-only involvement with itchy, flaking skin 1
- No visible inflammation or erythema 1
- Dry-appearing flakes (though actually greasy in composition) 5
Seborrheic Dermatitis (More Severe Form)
- Greasy, yellowish scaling with visible inflammation 6, 5
- Affects scalp, central face (especially nasolabial folds), eyebrows, chest, back, and other sebaceous areas 5, 4
- Erythema, pruritus, and sometimes a tight feeling 7
- In infants, may present as "cradle cap" 5
- Scalp involvement may be misdiagnosed as simple dandruff 8
Important clinical note: The scales are greasy, not dry, contrary to common perception 5. Stress can trigger flare-ups 5.
Associated Conditions and Risk Factors
Seborrheic dermatitis shows strong associations with:
- Seborrheic blepharitis: 95% of patients with eyelid involvement have seborrheic dermatitis elsewhere on the body 8, 3
- Rosacea: Co-occurs in 51% of patients with meibomian gland dysfunction 3
- Dry eye disease: Present in 25-40% of cases 2, 3
- Immunocompromised states: More pronounced in HIV infection, Parkinson's disease, and Down syndrome 2, 3
Diagnosis
Seborrheic dermatitis is a clinical diagnosis based on the characteristic location (sebaceous-rich areas) and appearance of lesions (greasy scaling with erythema) 4. No laboratory testing is typically required 4.
Key diagnostic features:
- Distribution in sebaceous areas (scalp, face, chest) 4
- Greasy yellow scales with underlying erythema 6, 5
- Chronic, relapsing course 3
Treatment Approach
First-Line Therapy
Topical antifungal agents targeting Malassezia are the mainstay of treatment 3, 4:
- Ketoconazole 2% cream: Apply once daily for facial/body involvement; twice daily for 4 weeks for seborrheic dermatitis 9
- Ketoconazole shampoo: For scalp involvement, provides significant improvement in flaking and erythema 10
- Selenium disulfide 1% shampoo: Effective for maintenance therapy after initial ketoconazole treatment, additionally reduces Staphylococcus species 10
Adjunctive Short-Term Therapy
Low-potency topical corticosteroids (such as hydrocortisone) may be used short-term alongside antifungals to control inflammation and itching 2, 3, 11. Critical caveat: Use corticosteroids only for short durations due to potential adverse effects 4.
Maintenance Strategy
Due to the chronic, relapsing nature of seborrheic dermatitis, ongoing maintenance therapy with antifungals is necessary to prevent recurrence 2, 3. Selenium disulfide provides additional benefit in preventing relapses by maintaining low Malassezia counts and reducing Staphylococcus levels 10.
Common Pitfalls to Avoid
- Mistaking greasy scales for dry skin: The scales appear dry but are actually greasy, requiring antifungal rather than simple moisturizing treatment 5
- Discontinuing treatment too early: Patients require 2-4 weeks of initial treatment and ongoing maintenance to prevent relapse 9, 10
- Prolonged corticosteroid use: Should be limited to short-term use only due to adverse effects 4
- Overlooking associated conditions: Always assess for blepharitis, rosacea, and dry eye, which frequently coexist 8, 2