Only the utmost quality of essential oils should be used in aromatherapy. The majority of essential oils produced in the world market are used in the food flavor and fragrance industry, so essential oils are often found on the market adulterated with similar essential oils, chemicals and synthetics, as well as extenders such as dipropylene glycol. Unfortunately, even the type used in food can be adjusted with chemicals from a natural source and still legally be called natural. Therefore, it is wise to purchase only from a reputable aromatherapy source.