PROBLEM TO BE SOLVED: To provide a vitamin K agent capable of delivering active vitamin K having high photostability and low phototoxicity even in a state where light shielding is not required and light shielding is difficult. SOLUTION: A vitamin K agent to be applied under light exposure, which comprises at least one kind of carboxylic acid esters of active vitamin K or a salt thereof, and an external preparation for skin, eye drops, and eye ointment using the same. [Selection diagram] Fig. 1【課題】遮光を必要とせず遮光が困難な状態においても、光安定性が高く且つ光毒性が低い活性型ビタミンＫ送達を可能にするビタミンＫ剤の提供。【解決手段】活性型ビタミンＫのカルボン酸エステル類またはその塩の少なくとも一種類からなる、光曝露下に適用されるビタミンＫ剤、及びそれを用いた皮膚外用剤、点眼剤、眼軟膏剤。【選択図】図１
