Effectiveness and safety of formalin 5% vs. combined salicylic acid 16.7% and lactic acid 16.7% in flexible collodion for common and plantar warts: a randomized clinical trial

Background: Warts are among the most common skin diseases with various recommended treatments, including topical ablation, chemotherapy, and immunotherapy. However, given the unsatisfactory response rate, complications, and recurrence, effective treatment remains controversial. This study compared formalin against an anti-wart compound containing salicylic acid and lactic acid. Methods: This clinical trial recruited 58 patients with wart lesions on hands and feet randomly divided into two groups of daily topical treatment: formalin 5% (n = 29) and anti-wart lotion containing salicylic acid 16.7% and lactic acid 16.7% in flexible collodion (n = 29) for eight weeks. Patient satisfaction and recovery were assessed and compared between the groups at weeks four and eight. Results: Patient satisfaction did not change significantly in either group (P > 0.05), and no significant difference was observed between the groups (P = 0.838). The number of wart lesions fell significantly after eight weeks in both groups (P < 0.001), with no significant difference between them (P = 0.225). There was no significant difference between the two methods in terms of side effects (P = 0.084). Conclusion: Both formalin and salicylic acid plus lactic acid lotion effectively treated plantar and common warts, and neither had any significant side effects. The treatment choice should be based on the patient’s age, the number of lesions, and the site affected.