A 40-year-old woman with no pre-existing hepatic disease developed a cutaneous allergic reaction to intramuscular vitamin K1. She received this medication prophylactically prior to surgery, developed severe localized, and subsequently generalized, dermatitis, beginning 5 days after administration of the Konakion Cremophor-EL form of vitamin K1 by intramuscular injection at four sites on her thighs. Investigation by patch and intradermal testing revealed delayed-type hypersensitivity to Konakion Cremophor-EL, Konakion Mixed Micelles and pure vitamin K1, but not Cremophor-EL vehicle alone. This case is unusual because the patient was also shown to be patch test positive to vitamin K3 sodium bisulfite.