Background Previous uncontrolled trials have suggested that oral terbinafine, an antimycotic allylamine compound, could be useful in the treatment of seborrhoeic dermatitis.

Objectives To investigate in a placebo‐controlled trial the clinical efficacy of oral terbinafine (Daskil®, Mipharm, Milan, Italy) in patients with moderate to severe seborrhoeic dermatitis.

Methods Sixty outpatients (mean ± SD age 37 ± 11 years; 32 men and 28 women) with moderate to severe seborrhoeic dermatitis were enrolled in a multicentre, randomized, placebo‐controlled, investigator‐blinded, parallel‐group, 12‐week study. After a 2‐week wash‐out period, enrolled patients were randomized to treatment with oral terbinafine 250 mg daily (n = 30) or placebo (moisturizing ointment) (n = 30) applied twice daily for 4 weeks (weeks 0–4). Patients were followed up for an additional 8 weeks after completion of treatment and were clinically evaluated at weeks 0, 2, 4 and 12 by an investigator unaware of the patient's type of treatment. The primary end‐point of the study was clinical evaluation of erythema, scaling and itching, each scored on a 0–3 scale. A global clinical score, representing the sum of each evaluated symptom, was also calculated.

Results Demographic and clinical data were equally balanced between the placebo and terbinafine groups. All enrolled patients concluded the study. At baseline, the mean ± SD global clinical score was 7·4 ± 1·3 in the placebo group and 7·7 ± 1·0 in the terbinafine‐treated group. At weeks 4 and 12 the mean ± SD global clinical score in the placebo group was 5·9 ± 1·7 and 6·3 ± 1·2, respectively, which was not significantly different from baseline. As compared with baseline values and the placebo group, terbinafine treatment significantly (P < 0·0001, Tukey–Kramer test) reduced the mean ± SD global clinical score (to 1·0 ± 1·1 at week 4, and 1·2 ± 1·4 at week 12), as well as the individual erythema, scaling and itching scores. No serious adverse events were recorded during the study in either group.

Conclusions This is the first controlled trial that has shown oral terbinafine to be effective in the treatment of moderate to severe seborrhoeic dermatitis. Clinical improvement following 4 weeks treatment with terbinafine was maintained 8 weeks after completing treatment.