Butylated Hydroxytoluene (BHT) is an antioxidant and preservative that's commonly used in perfumes and other cosmetics to extend shelf life and maintain product quality. It is usually dissolved in a mixture of fragrances or other compounds, and the typical dose is 0.1%. It dissolves in alcohol, vegetable oil, and DPG, but not well in water. Especially useful for volatile oils such as citruses.