Dandruff (Seborrhoeic Dermatitis) — Causes, Symptoms & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Dandruff (pityriasis simplex capitis) is an extremely common scalp condition characterised by chronic or recurrent white or greyish flaking of the scalp skin, often accompanied by itch. Seborrhoeic dermatitis is the more inflammatory form — affecting the scalp and characteristically also sebaceous gland-rich areas of the face (eyebrows, nasolabial folds, ears, eyelids) and chest. Both conditions are driven by the same pathophysiological process: overgrowth of Malassezia (formerly Pityrosporum) yeast species — particularly M. globosa and M. restricta — on sebaceous skin, leading to irritant fatty acid production, enhanced skin cell turnover, and inflammation. Dandruff affects up to 50% of the global adult population — making it one of the most prevalent dermatological conditions — though most cases are mild and manageable. It is not contagious or caused by poor hygiene.

The primary cause is Malassezia yeast (part of normal skin flora that becomes pathogenic in susceptible individuals) metabolising sebum lipids into oleic acid and other free fatty acids, which penetrate the stratum corneum and trigger an inflammatory response and accelerated keratinocyte turnover (desquamation — shedding). Risk factors: male sex (androgens stimulate sebaceous gland activity — dandruff is more common and severe in men), sebaceous skin type, Parkinson's disease (dramatically increased seborrhoeic dermatitis prevalence — up to 50-60% — due to seborrhoea from autonomic dysfunction and dopaminergic deficit), HIV/AIDS (severe, difficult-to-treat seborrhoeic dermatitis in immunosuppressed patients — often the presenting dermatological sign), other neurological conditions (epilepsy, head injury, spinal cord injury), emotional stress (exacerbates disease), cold dry weather (worsens symptoms in winter, improves in summer with UV exposure), infrequent shampooing (allows scale build-up), and certain medications.

Scalp dandruff: white or greyish loose, dry flakes falling from the scalp onto hair and clothing (most visible on dark clothing), associated scalp itch (pruritus — often mild to moderate), and scalp dryness. Seborrhoeic dermatitis of the scalp: in addition to flaking, well-defined red, greasy-looking patches with yellowish-white adherent scales distributed in the hair-bearing areas of the scalp, scalp margins, and behind the ears. Facial seborrhoeic dermatitis: erythema, scaling, and greasy crusts affecting eyebrows (brow scaling), nasolabial folds (skin creases beside the nose), external ear canal, eyelid margins (seborrhoeic blepharitis — crusting and redness of the eyelid margins), and hairline. Trunk seborrhoeic dermatitis: oval, scaly, erythematous patches in a 'petaloid' or 'Christmas tree' distribution on the chest and upper back. The condition is typically chronic with remissions and flares, rather than a single episode.

Dandruff and seborrhoeic dermatitis are diagnosed clinically — no investigations are required in typical presentations. The clinical picture — characteristic distribution (scalp, face in sebum-rich areas, chest), greasy yellowish scale, and associated erythema — is diagnostic. Scalp dermoscopy: reveals follicular plugging, yellow scale, and superficial perifollicular vessels in seborrhoeic dermatitis. Differentiation from other scalp conditions: Psoriasis — well-demarcated, thicker, dry, silvery-white scaling plaques; Koebner phenomenon; may have nail and joint involvement. Tinea capitis (scalp ringworm) — patchy alopecia, scaling, broken hairs; more common in children; confirm with scalp skin scrapings and fungal culture/microscopy. Contact dermatitis — history of new hair products or dyes; eczematous rather than scaly. Atopic eczema — personal or family history; flexural distribution. Skin biopsy is rarely needed but shows spongiosis with neutrophilic exocytosis in seborrhoeic dermatitis.

Medicated antifungal shampoos are the mainstay of treatment for dandruff and scalp seborrhoeic dermatitis: Ketoconazole 2% shampoo (Nizoral) — most effective antifungal agent; initially 2x weekly for 4 weeks (leave on for 3-5 minutes), then weekly for maintenance; reduces Malassezia burden directly. Zinc pyrithione shampoo (Head and Shoulders Active or prescription formulations): antibacterial and antifungal; gentler; can be used 3x weekly long-term. Selenium sulphide 2.5% shampoo: antifungal and sebum-reducing; leave on for 2-5 minutes; effective but can discolour blonde or chemically treated hair. Coal tar shampoo: anti-inflammatory, antiproliferative, antifungal; effective but malodorous; may stain. Ciclopirox olamine shampoo: broad-spectrum antifungal; good evidence for seborrhoeic dermatitis. Topical corticosteroids (scalp preparations — betamethasone valerate 0.1% lotion, fluocinolone acetonide shampoo) for inflamed, symptomatic seborrhoeic dermatitis: reduce erythema and itch; use intermittently to avoid skin atrophy. Facial seborrhoeic dermatitis: ketoconazole 2% cream or miconazole cream applied to affected areas; low-potency topical corticosteroids (hydrocortisone 1%) for short-term itch control; calcineurin inhibitors (tacrolimus 0.1% ointment, pimecrolimus 1% cream) are steroid-sparing options for facial disease (avoid corticosteroid side effects on face). Selenium sulphide or sodium sulphacetamide lotions for trunk disease.

Secondary bacterial infection (severe seborrhoeic dermatitis with extensive crusting and excoriation can become secondarily infected with Staphylococcus aureus — presenting as impetiginised, crusted, weeping dermatitis requiring topical or oral antibiotic treatment). Seborrhoeic blepharitis (seborrhoeic dermatitis affecting the eyelid margins — causes chronic eye irritation, recurrent conjunctivitis, and meibomian gland dysfunction; treated with lid hygiene, topical antibiotics, and occasionally oral tetracyclines for severe cases). Alopecia (severe long-standing scalp seborrhoeic dermatitis with significant inflammation and intense scratching may cause temporary hair shedding — telogen effluvium — which is generally reversible with effective treatment of the scalp condition). Psychosocial impact (visible scalp and facial scaling on darker skin tones causes significant embarrassment, reduced self-confidence, and social withdrawal — quality of life impact can be disproportionate to clinical severity, warranting psychological support alongside medical treatment).

Regular shampooing: washing the scalp 2-3 times weekly with an antifungal or anti-dandruff shampoo prevents Malassezia build-up and scale accumulation. Do not leave shampoo on for less than 3-5 minutes — adequate contact time is essential for efficacy. Rotating between two different active ingredients (e.g., ketoconazole and zinc pyrithione) every few months prevents tolerance and maintains efficacy. Maintain the scalp clean but avoid over-washing with harsh regular shampoos that may disrupt the scalp's natural barrier. Reduce stress — a well-established trigger for flares. Sunlight (UV radiation) has a mild beneficial effect on seborrhoeic dermatitis — some controlled outdoor exposure may help. Avoid thick, occlusive hair oils (coconut oil, mineral oil) which provide substrate for Malassezia growth. Hair gel, wax, and pomades can similarly worsen dandruff — use sparingly. In patients with HIV or Parkinson's disease, more aggressive and frequent antifungal treatment is needed.

See a GP or dermatologist if: dandruff or scalp scaling is severe or not improving after 4-6 weeks of regular use of over-the-counter antifungal shampoo, the scalp is very inflamed, itchy, or crusted, there is hair loss associated with the scalp condition, facial involvement (seborrhoeic dermatitis of eyebrows, nasolabial folds, or eyelids) requires treatment, or the diagnosis is uncertain. Seek urgent review if you are immunocompromised (HIV, organ transplant) and develop extensive seborrhoeic dermatitis — this may indicate significant immunosuppression. Tinea capitis (fungal scalp infection causing hair loss in children) is a medical condition distinct from dandruff and requires oral antifungal treatment — always see a doctor for scalp scaling with hair loss in a child.