Between 1964 and 1994, at least 52 patients with cutaneous adverse effects of vitamin K have been described in the European and North American literature, A review of the details of these patients is given and 2 new cases reported. Adverse effects are seen not only in patients with liver-function disturbances but also in patients without liver diseases, and occur mostly after intramuscular or subcutaneous administration of vitamin K₁, independent of the total dose. Patch and intracutaneous tests often give positive reactions. The mechanism of action is probably in many patients a delayed-type hypersensitivity reaction.