Ketoconazole

What it is

Ketoconazole is an imidazole antifungal. As a shampoo it is sold at 1% over the counter and at 2% as a stronger product. The strength and the prescription status differ between countries, so check the pack. The oral tablets are a separate, higher-risk drug (see safety below).

How it works

Ketoconazole blocks the fungal production of ergosterol, which is why it is active against the Malassezia yeasts that live on the scalp and are linked to dandruff and seborrheic dermatitis. Reviews also credit it with some anti-inflammatory activity and a reduction in casual sebum levels (Pierard-Franchimont 1998). How it might help hair growth is not settled: the original human trial suggested a microbial and inflammatory contribution to pattern hair loss, and mouse work suggests a growth-promoting effect of unclear mechanism (Jiang 2005).

What the studies show

• In 575 treated people with scalp seborrheic dermatitis or dandruff, a 2% ketoconazole shampoo used twice weekly for 2-4 weeks gave an excellent response in 88%. In the prevention phase (312 people), relapse within 6 months was 19% with weekly ketoconazole versus 47% with placebo. The trial was multicentre and double-blind (Peter 1995).
• In 331 people with severe dandruff or seborrheic dermatitis, ketoconazole 2% was significantly better than zinc pyrithione 1% over 4 weeks, with fewer recurrences; both were well tolerated (Pierard-Franchimont 2002).
• In 154 people, a ciclopirox 1.5% plus salicylic acid 3% shampoo and ketoconazole 2% both improved dandruff and seborrheic dermatitis over 4 weeks; only the ciclopirox combination significantly reduced itch (Squire 2002).
• In men with pattern hair loss, a 2% ketoconazole shampoo improved hair density, hair size and the share of growing hairs about as much as 2% minoxidil, and sebum fell. It was a controlled trial, but the number of people and the funding are unclear from the abstract (Pierard-Franchimont 1998).
• A systematic review of topical ketoconazole for pattern hair loss found 7 papers (2 animal studies on 40 animals, 5 human studies on 318 people). Human studies showed increased hair-shaft diameter, but there was no large randomized trial, and the authors called for one (Fields 2020).
• In mice, 2% ketoconazole daily for 3 weeks regrew clipped coat faster than vehicle (p < 0.01) (Jiang 2005).
• A 2024 expert consensus (7 experts, 131 papers) names antifungals and anti-inflammatory topicals as the mainstay for scalp seborrheic dermatitis and notes no approved therapy exists for moderate-severe disease (Vano-Galvan 2024).

For dandruff and seborrheic dermatitis, several randomized trials show benefit, so the evidence is strong. For hair loss the human evidence is small, short and partly uncontrolled, so the evidence is limited at best.

How it's used in studies

• Dandruff and seborrheic dermatitis: the 2% shampoo was used twice weekly for 2-4 weeks, then once weekly or on alternate weeks for prevention (Peter 1995).
• Hair loss: the 2% shampoo was typically used two to three times a week, left on the scalp for several minutes before rinsing, as an add-on to standard therapy. Regimens vary between studies (Fields 2020).
• Leave the lather on the scalp for the time stated on the label so the drug has contact with the skin.

Side effects and safety

• Topical use is generally well tolerated. Mild irritation, dryness, itching, a change in hair texture and, rarely, contact dermatitis are reported.
• Oral ketoconazole is a different, higher-risk drug. Regulators restricted the tablets because of liver injury, adrenal suppression and drug interactions. Do not source oral ketoconazole for hair loss.
• If the scalp is not better after about four weeks, the problem may not be dandruff, so get it looked at.

Bottom line

For visible flakes with itch, ketoconazole shampoo is one of the strongest options and was ahead of zinc pyrithione in a head-to-head trial in severe cases. Use it two to three times a week until clear, then weekly. For hair loss, treat it as an optional add-on to proven treatments such as minoxidil and finasteride, not a replacement; the evidence is promising but small. It costs very little. Alternating it with a gentle shampoo helps if it dries your lengths, especially for coily or colour-treated hair. Discuss with a doctor.

Fun facts

• In the 1998 trial, a ketoconazole shampoo moved hair density and the proportion of growing hairs about as much as 2% minoxidil. It remains one of the few shampoo-format ingredients with any hair-density data (Pierard-Franchimont 1998).