Provided is a skin moisture-retention improving agent that contains, as an active ingredient, a specific cyclic dipeptide having amino acids as structural units, or a salt thereof. Also provided are a use of said agent to improve moisture-retention in skin, a method for improving the moisture-retention of skin, and the like. The specific cyclic dipeptide was found to have an action of remarkably improving the moisture-retention of skin. The agent according to the present invention provides a novel agent for improving the moisture-retention of skin that contains, as an active ingredient, a cyclic dipeptide having high fat-solubility and excellent gastrointestinal permeability and membrane permeability.本發明之課題係提供含有以胺基酸作為構成單位之特定的環狀二肽或其鹽作為有效成分之皮膚保濕機能改善劑、該劑用於改善皮膚保濕之用途、以及改善皮膚的保濕機能之方法等。本發明之解決手段為發現特定的環狀二肽係具有顯著地改善皮膚的保濕機能之作用。本發明之劑係提供脂溶性較高且消化道穿透性或膜穿透性優異的以環狀二肽作為有效成分之新穎的皮膚保濕機能改善劑。
