Delayed hypersensitivity to 5-fluorouracil following topical chemotherapy of cutaneous cancers

Skin tests to various common antigens, dinitrochlorobenzene, and 5-fluorouracil (5-FU) were performed on patients being treated for cutaneous neoplasms with topical 5-FU cream. Eleven of 15 patients tested both before and after therapy converted from skin test negative to positive with respect to 5-FU. This conversion correlated with positive dinitrochlorobenzene skin tests and therapeutic cure. The relation between the induction of delayed hypersensitivity reactions to 5-FU following treatment with topical 5-FU and the cure rate for cutaneous neoplasms showed a trend toward correlation.