Third-degree chemical burn for hand wart

Cutaneous warts, caused by human papillomavirus (HPV), are commonly treated with various systemic and topical therapies, including acid-based solutions. However, misuse of caustic agents like formic acid can result in serious complications. We report a case of a 44-year-old male who developed a third-degree chemical burn on the dorsal aspect of the right second finger after improper use of an over-the-counter 85% formic acid solution for wart treatment. Despite the product’s recommendation for limited weekly use, the patient applied it twice daily. A necrotic wound developed, necessitating surgical debridement and eventual reconstruction with two local rotational Yin-Yang flaps. Full functional recovery was achieved, with a QuickDASH score improving from 61.4 preoperatively to 0 at 13 months postoperatively. Although acid-based treatments like formic acid are effective for wart removal, unsupervised use can lead to chemical burns and deep tissue damage. Management involves debridement and appropriate reconstructive techniques based on wound depth and location. For dorsal finger defects, local flap options such as Yin-Yang flaps are advantageous, offering single-stage closure without donor site morbidity. This case highlights the importance of medical supervision when using caustic wart treatments and highlights effective surgical strategies for managing resultant injuries.