Scalp Condition Misdiagnosis (Dandruff vs Dry Scalp vs Seborrheic vs Psoriasis)

Four conditions routinely get lumped together as 'dandruff' in consumer discourse. They have different causes and need different treatments. ## Dry scalp - **Flakes**: small, powdery, white. - **Inflammation**: none. - **Skin feel**: tight, itchy, not oily. - **Cause**: insufficient sebum; cold air, low humidity, over-washing, harsh shampoos. - **Treatment**: reduce shampoo frequency, use moisturising conditioners, apply leave-in oils or humectants. **Antifungal shampoos (zinc pyrithione, ketoconazole) make this WORSE** by further stripping oils. ## Dandruff proper (*Pityriasis simplex capillitii*) - **Flakes**: larger, oily, yellowish or white. - **Inflammation**: minimal redness. - **Skin feel**: oily scalp, itchy. - **Cause**: Dandruff Biology and the Malassezia Mechanism, immune overreaction to oleic acid. - **Treatment**: antifungal shampoos — zinc pyrithione for maintenance, selenium sulfide for moderate, ketoconazole 2% for severe. 10-15 minute contact time. - **Prevalence**: ~50% of adults. ## Seborrheic dermatitis - **Flakes**: greasy yellow, scaly. - **Inflammation**: visible redness, sometimes oozing. - **Distribution**: scalp + eyebrows, nasolabial folds, behind ears, chest, beard area. - **Skin feel**: burning, itching, sometimes painful. - **Cause**: same Malassezia mechanism as dandruff, with more severe inflammatory response. Associated with Parkinson's disease, HIV, depression, stress. - **Treatment**: ketoconazole 2%, sometimes combined with topical steroids for flares. Ciclopirox is an alternative. - **Prevalence**: 3-12% of adults. ## Scalp psoriasis - **Flakes**: thick, silvery, adherent plaques. - **Inflammation**: well-defined red plaques with sharp borders. - **Cause**: autoimmune — NOT fungal. T-cell mediated hyperproliferation. - **Treatment**: topical corticosteroids, calcipotriol (vitamin D analogue), coal tar, phototherapy, biologics for severe. Antifungals do nothing. - **Prevalence**: 2-3% of adults; 50% of people with body psoriasis also have scalp psoriasis. ## Diagnostic quick reference | Feature | Dry | Dandruff | Seb Derm | Psoriasis | |---|---|---|---|---| | Flake size | Small | Medium | Medium-large | Large | | Oil | Dry | Oily | Greasy | Varies | | Redness | None | Minimal | Moderate | Marked | | Border | Diffuse | Diffuse | Diffuse | Sharp | | Cause | Moisture | Fungus | Fungus+inflam | Autoimmune | | First-line | Moisturiser | Zinc pyrithione | Ketoconazole | Steroid | ## Why misdiagnosis is common - Over-the-counter marketing conflates all flaky conditions as 'dandruff.' - Many people self-diagnose and use antifungals indiscriminately. - Overlap is real: someone can have both seborrheic dermatitis and psoriasis. - Dermatologist visits are gated by cost and wait times. When in doubt, a dermatology consult can distinguish via dermatoscopy and response to trial treatment. For persistent cases not responding to OTC products, the treatment algorithm branches based on which of these four is actually present.