Itchy scalp

Key takeaways

• Itch is a symptom with many causes, and the dermatology approach is to sort them first. A systematic review proposes splitting scalp itch into itch with visible skin lesions versus without, and with or without hair loss, and thinking of the common causes first (Vazquez-Herrera 2018).
• The commonest cause is dandruff or seborrheic dermatitis. See dandruff and seborrheic dermatitis. Antifungal shampoos reduce itch: 95.6% of subjects reported less itch in one open-label selenium sulfide study (Turcu 2023, industry-linked).
• Other causes with visible skin changes include psoriasis (scalp psoriasis), folliculitis (scalp folliculitis), atopic or contact dermatitis, lice and fungal infection (tinea capitis, mainly in children).
• Contact allergy to hair products is real. Para-phenylenediamine (PPD) in hair dye is a classic strong allergen (Mukkanna 2017; Palaniappan 2023). Preservatives such as methylisothiazolinone cause allergic reactions in some people, though sensitisation in New Zealand was falling (Lee 2024). Never test a "natural" or black-henna dye that contains PPD.
• Itch without any visible skin change can be a sensitive scalp or scalp dysesthesia: burning, itching, pain or tingling, sometimes with hair shedding. Triggers include stress, topical products and nerve causes (Guerra-Tapia 2023; Ju 2022). "Trichodynia" is a symptom description with diverse causes (Trueb 2021).
• In a 2005 trial, 3% salicylic acid plus 1% hydrocortisone gave the best relief of scalp itch among the keratolytic, steroid and combination regimens compared (Draelos 2005).
• See a doctor for persistent itch, hair loss, sores, swelling or pain, or for children with patchy scaling.

The science

Neuropathic itch arises from nerve irritation rather than skin inflammation, and reviews list causes from cervical spine disease and small-fibre neuropathy to scars and post-infectious states (Ju 2022). A mechanism involving nerve signals linking stress, nerves and skin immune cells has been proposed for trichodynia, but this is a hypothesis (Trueb 2021). Sensitive scalp is subjective, with no lab or biopsy test, and may be primary (no scalp disease) or secondary to psoriasis, dermatitis or atopic dermatitis (Guerra-Tapia 2023).

What it means by hair profile

• Dry, flaky or itchy scalp: first consider dandruff rather than "dryness".
• Coily hair and infrequent washing: scalp buildup and traction can both itch; see traction and hairstyles.
• Fine or oily hair: itch often follows heavy product use, so check for fragrance or preservative sensitivity.
• Colourists and dye users: itch within 48 hours of dyeing suggests contact allergy. Stop and seek advice.

Myths and facts

• Myth: itch means a dry scalp, so use oil. Fact: oils can worsen yeast-related itch and mask allergy.
• Myth: sulfate-free shampoo cures a sensitive scalp. Fact: no trial shows this, and mildness depends on the whole formula (see how shampoo works).

Bottom line

Check for flakes: if present, start an antifungal shampoo two to three times a week for 4 weeks. Pause new products such as dyes, scrubs and essential-oil treatments, and check ingredient lists for known allergens. Rinse thoroughly. If itch persists with a normal-looking scalp, or is burning or painful, ask a dermatologist about sensitive scalp or dysesthesia. Patch testing identifies contact allergens. Discuss with a doctor.