What is Seborrhoeic Dermatitis
Seborrhoeic dermatitis is a common chronic inflammatory skin condition that affects sebaceous gland-rich areas of the body, presenting with greasy yellowish scaling, itching, and erythematous patches, with secondary inflammation from Malassezia yeast. 1
Clinical Presentation
The condition manifests with characteristic features that vary by location and skin tone:
- Classic appearance: Symmetric, poorly defined erythematous patches with yellow, oily scales and fine superficial desquamation (flaking) 2
- Greasy yellowish scaling with associated itching 1
- Distribution: Predominantly affects the scalp, central face, ears, and other sebaceous areas of the skin 1
Important Presentation Variations
In patients with darker skin tones, erythema may be less apparent, and the presenting sign is often postinflammatory pigmentary changes with hypopigmented, slightly scaly areas 2, 3. This is a critical diagnostic pitfall—clinicians must actively look for pigmentary alterations rather than relying solely on erythema detection.
Pathophysiology
The condition involves a complex interplay of three key factors 4:
- Microbiome dysbiosis: Malassezia yeast overgrowth and alterations in bacterial composition
- Dysregulated inflammatory responses in the skin
- Skin barrier dysfunction
High-Risk Populations
Seborrhoeic dermatitis is significantly more pronounced in specific patient populations 1:
- Patients with Down syndrome
- Patients with HIV infection
- Patients with Parkinson's disease
Additionally, 95% of patients with seborrhoeic blepharitis also have seborrhoeic dermatitis, and 74% of patients with primary meibomitis have seborrhoeic dermatitis 5.
Differential Diagnosis Considerations
Seborrhoeic dermatitis can mimic or coexist with several conditions 1, 3:
- Atopic dermatitis (eczema): Distinguished by chronic pruritus typically starting in childhood with involvement of multiple body areas, showing erythema, xerotic scaling, lichenification, and hyperpigmentation
- Psoriasis: Has characteristic skin lesions with different scaling patterns
- Rosacea: May coexist in 51% of cases 5
- Contact dermatitis: Requires patch testing if suspected
Clinical Impact
The condition significantly impacts quality of life, particularly when involving the facial region with pruritus and dyspigmentation 4. It follows a chronic relapsing course 2, requiring ongoing management rather than curative treatment.