Vitamin K injection site reaction is a rare but well-reported sequela of intramuscular injection of fat-soluble phytonadione, or vitamin K1. Vitamin K injections are commonly given to patients with underlying liver disease, a vitamin K-dependent coagulopathy, or a supratherapeutic international normalized ratio (INR) in the setting of oral Coumadin (warfarin) therapy.

Reactions are thought to be caused by a type IV delayed type hypersensitivity with two distinctive phenotypes: eczematous and sclerodermoid. One reported case of a diffuse rash has been attributed to vitamin K injection.

Eczematous reactions tend to appear within a week of injection and resolve over the course of a month. The reaction is localized to the general proximity of injection. Sclerodermoid changes can be seen several months after injection and persist for years despite treatment. Preceding inflammation may or may not be observed.

Previously, it was thought that patients with underlying liver disease who received phytonadione injection were at an elevated risk to develop injection site reactions. More recent review of existing case reports has found this not to be the case.

Patch testing to vitamin K has not been found to be beneficial in predicting this reaction, although intradermal prick testing has been positive in affected patients in one study.