Urea is a white crystalline compound naturally produced as the major end product of protein metabolism in the human body. It is one of the key components of the natural moisturizing factor (NMF) and an active humectant in skincare. As a widely used substance with a long history of clinical application, urea is regarded as an essential moisturizing and keratolytic agent in dermatology. Modern research has confirmed that it possesses various biological activities, including moisturizing, keratolytic, antipruritic, and skin barrier-enhancing properties.