Selenium or Ketoconazole Shampoo?Four Trial Checks

A 2024 trial compared shampoos in 64 adults with moderate-to-severe scalp seborrheic dermatitis: 35 received selenium, 29 ketoconazole.¹

Compare formulas and schedules

Dercos contained 1% selenium disulfide plus salicylic acid, used three times weekly; Nizoral contained 2% ketoconazole, used twice weekly. Different formulas and schedules prevent attributing results to selenium alone.¹

Separate improvement from superiority

At 28 days, average severity score fell 71% versus 69% from baseline. No significant clinical difference between shampoos was found; this did not establish equivalence.¹

Check the reporting limits

Vichy funded the trial; two authors were employees. Withdrawal counts, missing-data handling and adverse-event counts aren’t reported. Four weeks cannot establish long-term safety.¹

A separate 2026 trial studied 0.6% micronized selenium against 2% ketoconazole for six weeks in 87 participants. Both groups improved, without significant differences in the clinical outcomes. This manufacturer-supported study used a different formula; it does not make the 2024 results transferable to every selenium shampoo.²

Read your bottle’s directions

The US Dercos label lists 0.6% micronized selenium sulfide. Its directions say at least twice weekly or as directed by a doctor: shake, wet hair, apply a small amount, massage, leave for two minutes, then rinse well. Avoid eye contact; rinse thoroughly if contact occurs. Stop and ask a doctor if symptoms worsen or don’t improve with directed use.³

US over-the-counter Nizoral contains 1% ketoconazole, a different strength from the study comparator. Its label calls for use every three or four days for up to eight weeks in people 12 or older; younger children need a doctor. Avoid broken or inflamed scalp and eye contact. Do not use it if allergic to its ingredients. Stop and ask a doctor if a rash appears, symptoms worsen, or they do not improve within two to four weeks. Ask a doctor before use during pregnancy or breastfeeding.⁴

A dermatologist may adjust washing frequency for hair texture. The AAD describes two or three weekly washes for straight or wavy hair, potentially once weekly for curly or tightly coiled hair, and emphasizes the prescribed contact time. Persistent symptoms may require prescription treatment rather than more frequent washing.⁵

Our dandruff ingredient guide explains the broader shampoo categories. Hair, Everywhere discusses dandruff and scalp warning signs in “The Crown.” See the book.