Dinitrochlorobenzene (DNCB) is a topical immunotherapy agent that works by deliberately creating a local allergic reaction, prompting the immune system to recognize and attack HPV-infected wart tissue. It is typically reserved for refractory or multiple warts that have not responded to standard treatments like salicylic acid or cryotherapy. Treatment is performed in a clinical setting—first sensitizing the skin to DNCB, then applying it to the wart at follow-up visits to stimulate an immune response. As the body reacts, the wart may become inflamed, crust, and gradually clear over several weeks. Because DNCB is a strong sensitizer with potential carcinogenic and mutagenic concerns, its use is infrequent today and generally limited to specialized dermatology settings or replaced by safer alternatives.