Background Viral warts are common dermatological diseases; although the rate of spontaneous recovery is high, it usually takes a long time, and some patients might not show this spontaneous healing. Zinc has an important effect on the immune system and it has been used as an immunomodulator to treat a variety of skin disorders.

Objective To assess whether oral zinc was effective in treating viral warts of patients evaluated between May 1999 and April 2000.

Patients and methods This was a placebo‐controlled clinical trial. Eighty patients with viral warts (common, plantar and plane) were all resistant to all forms of treatment. Each patient had > 15 warts. Forty patients were treated by oral zinc sulphate at a dose of 10 mg kg−1 daily up to 600 mg day−1 and followed‐up for resolution of their warts and for any evidence of recurrence for 2–6 months. Another 40 patients were given a placebo oral treatment in the form of glucose, and followed‐up for the same period.

Results Only 23 patients of the first group (zinc treated) and 20 patients of the second group (placebo treated) completed the study. In all patients the serum level of zinc was low. In the zinc‐treated group, the overall response was complete clearance of warts observed in 20 patients (86·9%) after 2 months of treatment. Fourteen patients (60·9%) showed complete disappearance of their warts after 1 month. Three patients (13·3%) failed to respond to the treatment after 2 months of therapy. The response to treatment was directly related to the increment in serum zinc level. No patient of the placebo‐treated group showed any response.

Conclusions We conclude that zinc sulphate at a dose of 10 mg kg−1 daily seems to be a highly efficacious therapeutic option for recalcitrant viral warts and proved to be safe with few adverse effects.