VHOSPITAL.CLINIC · Differential Diagnosis
Psoriasis vs Seborrheic Dermatitis
Clinical comparison — shared symptoms, key differences, distinguishing diagnostic tests, treatment pathways, and when to seek urgent evaluation.
Condition Overview
Condition A
Psoriasis
Psoriasis is a chronic autoimmune skin condition that causes rapid skin cell turnover, resulting in thick, red, scaly patches (plaques). It can affect any part of the body and is associated with psoriatic arthritis. Stress, infections, and certain medications can trigger flares.
Condition B
Seborrheic Dermatitis
Seborrheic dermatitis is a chronic inflammatory skin condition causing scaly patches and red skin, particularly on the scalp (dandruff), face, and chest. Malassezia yeast overgrowth plays a role; antifungal shampoos and mild topical steroids are effective.
Shared Symptoms — Why They're Confused
Both conditions present with 3 overlapping symptoms, making clinical differentiation essential.
Key Clinical Differences
Psoriasis
- Well-demarcated silvery-scaled erythematous plaques
- Extensor surfaces, scalp, nails (pitting, onycholysis)
- Strong genetic component; Koebner phenomenon
- Scalp disease: thick, adherent scales
Seborrheic Dermatitis
- Greasy, yellowish scales on sebaceous areas (scalp, face, chest)
- Dandruff is the mildest form
- Associated with Malassezia yeast overgrowth
- No nail involvement; no extensor plaques
Distinguishing Diagnostic Tests
| Test | Psoriasis | Seborrheic Dermatitis |
|---|---|---|
| Location and scale quality | Extensor surfaces, scalp, nails — silvery adherent scale | Scalp, nasolabial folds, brows, chest — greasy yellowish scale |
| Nail examination | Nail pitting, onycholysis, oil drop sign — psoriatic nail disease | Normal nails |
| Response to antifungal | No response to ketoconazole — not fungal | Improves with antifungal shampoo/cream (targets Malassezia) |
Treatment Approaches
Psoriasis
- •Topical corticosteroids + vitamin D analogues (calcipotriol)
- •Biologics (anti-IL-17, anti-IL-23) for moderate-severe disease
- •Phototherapy (NB-UVB)
Seborrheic Dermatitis
- •Ketoconazole or selenium sulphide shampoo
- •Topical corticosteroids for inflammatory flares
- •Zinc pyrithione maintenance
When Doctors Consider Each Diagnosis
🔵 Consider Psoriasis when:
- →Silvery scales on extensor surfaces, nail changes, Koebner, no antifungal response
🟢 Consider Seborrheic Dermatitis when:
- →Greasy scales on sebaceous areas, dandruff, responds to antifungal
Explore Each Condition in Detail
Related Clinical Pages
Psoriasis
Medical References
Content on this page is informed by evidence-based clinical sources including:
- World Health Organization (WHO)Global health guidance and disease classification
- National Health Service (NHS)UK clinical guidelines and patient information
- National Institute for Health and Care Excellence (NICE)Evidence-based clinical practice guidelines
- Centers for Disease Control and Prevention (CDC)US public health data and clinical recommendations
- PubMed – NCBIPeer-reviewed biomedical literature and clinical studies
- Cochrane LibrarySystematic reviews and meta-analyses in evidence-based medicine
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