The objective is to investigate whether diphencyprone (DPCP), a chemical which can cause contact allergy on the skin in about 95% of people, can stimulate the immune system to destroy these melanoma cells. DPCP is frequently used in dermatology as a treatment for autoimmune hair loss (alopecia areata) and warts, where it also stimulates an immune attack on the wart virus. As melanoma is a tumour which is known to be particularly susceptible to immune attack, it is hoped that DPCP treatment will be helpful to patients with otherwise untreatable secondary melanoma in their skin. There have so far been a handful of published case reports of patients in whom DPCP has been helpful for melanoma.