by David Stewart, Ph.D., R.A. People who use adulterated or synthetic oils worry about shelf life. Some British references on aromatherapy say one should throw away their oils every six months and purchase a fresh quantity. Such advice may be valid for certain carrier blend oils, but is not valid for genuine, unadulterated premium-grade oils that are the products of proper distillation. In order to discuss shelf life, you need to distinguish between various classes of scented oils. There are four types of fragrant oils to consider: (1) Essential oils (distilled). (2) Expressed oils (usually citrus); (2) Absolutes (solvent extractions); and (4) Carrier Blend Oils (essential oils in a fatty base). The shelf lives of these four classes of aromatic oils are different. While expressed, absolute, and carrier blend oils contain large molecules along with their small aromatic ones, pure essential oils obtained entirely by distillation contain only small molecules. … Continue reading →