Leupeptin, a naturally occurring protease inhibitor, has potential applications in cosmetics due to its anti-inflammatory properties and ability to inhibit various proteases. It can be used in skincare products to help reduce inflammation and provide soothing effects to the skin. Additionally, Leupeptin's ability to inhibit proteases could contribute to the prevention of skin degradation and promote skin health by preserving the structural integrity of proteins in the skin matrix. Therefore, Leupeptin's applications in cosmetics may include anti-inflammatory and skin-protective effects, making it a valuable ingredient for products aimed at reducing skin irritation and promoting a healthy skin environment. It is a reversible, competitive inhibitor that targets serine and cysteine proteases, including trypsin, plasmin, calpain, papain, and cathepsins B, H, and L.