Butylated Hydroxyanisole (BHA) is a synthetic antioxidant commonly used as a preservative in skincare products. It prevents the oxidation of oils and fats which helps extend the shelf life of products and inhibit the development of rancidity and spoilage. BHA is sometimes included in formulas for its antioxidant properties and its potential to stabilize and protect certain ingredients from degradation because of exposure to air and light.