NEW YORK (Reuters Health) – Treating common warts with topical salicylic acid is less effective than cryotherapy with liquid nitrogen, a Dutch study has shown. Plantar warts, however, are as likely to clear with either treatment, or none.

Generally, “There is a lack of high quality evidence for many minor ailments in daily practice for physicians,” Dr. Sjoerd C. Bruggink told Reuters Health in an email. “Guidelines on wart treatment suggest salicylic acid because evidence on cryotherapy is sparse and of low quality. However, cryotherapy is widely used for treatment of common and plantar warts in daily practice.”

Dr. Bruggink at Leiden University Medical Center, the Netherlands, and colleagues conducted a three-arm randomized controlled trial of treatments for common and plantar warts in 250 primary care patients, age 4 to 79 years. They were randomly assigned to cryotherapy with liquid nitrogen, topical application of salicylic acid, or a wait-and-see approach.

As reported in the Canadian Medical Association Journal online, overall cure rates at 13 weeks, in 240 evaluable patients, were 39% in the cryotherapy group, 24% in the salicylic acid group and 16% in the wait-and see group. The likelihood of cure was significantly higher (relative risk 1.62) with cryotherapy than salicylic acid.

Among the 116 patients with common warts, corresponding cure rates were 49%, 15% and 8%. The cure rates for plantar warts were not significantly different at 30%, 33% and 23% in the three arms, respectively, according to the report.

“For plantar warts, cryotherapy or salicylic acid are not effective,” Dr. Bruggink commented. “In children, around 50% of patients cure after 3 months, also without treatment; in adolescents and adults only few warts cure, also after treatment.”

Side effects such as pain, skin irritation or blistering were more common with cryotherapy than salicylic acid. However, “69% of participants were satisfied with treatment after cryotherapy, as compared with 24% after salicylic acid treatment and 22% after the wait-and-see protocol,” the team reports.

Dr. Bruggink and colleagues conclude, “Although earlier evidence favoured topical salicylic acid application over cryotherapy for the treatment of cutaneous warts, the results of our randomized controlled trial provides evidence to support the use of cryotherapy over salicylic acid treatment, for common warts only.”

Reference:

Cryotherapy with liquid nitrogen versus topical salicylic acid application for cutaneous warts in primary care: a randomized controlled trial

CMAJ 2010;