Contact immunotherapy has been shown to be effective for warts. Two previous studies on the use of squaric acid dibutylester (SADBE) for warts have reported widely divergent cure rates (10% and 60%).

Our purpose was to determine the efficacy of SADBE in the treatment of recalcitrant warts.

We treated 29 patients with SADBE for warts that were resistant to other therapies. The patient population had warts for a mean duration of 2.1 years. Patients were sensitized with 1% or 2% SADBE in acetone under occlusion, the treated with 0.5% to 5% SADBE applied to their warts every 2 to 4 weeks in the office.

Clearing of all warts was seen in 20 of 29 patients (69%), improvement in 3 patients (10%), and no change in 6 patients (21%). For the cured patients, mean duration of treatment was 4.2 months (range, 1 to 12 months) and mean number of treatments was 5.7 (range, 2 to 15). Adverse effects included acute contact dermatitis with 6 patients experiencing blisters and one experiencing hypopigmentation.

SADBE treatment is worth considering in patients with recalcitrant warts, especially in those who tolerate painful procedures poorly.