Cold pressed essential oils, such as citrus oils, begin to lose their fresh, sweet or tart aroma at about a year after being pressed.
Even with the best of care, within twelve to twenty four months any cold pressed citrus oil will be past using. Steam distilled essential oils, which make up the vast majority of essential oils, have no true shelf life, in that they do not ever “go bad”. Essential oils contain no fatty acids and essential oils form an environment too hostile for most bacteria, mold or yeast to survive in. Consequently, essential oils are not particularly subject to spoilage and rancidity. They do not “turn” and produce an offensive odor like spoiled milk or rancid vegetable oil. Rather, over a period of many years the volatile aroma compounds making up an essential oil very slowly degrade and gradually fade away to nothing.
Some essential oils, such as Patchouli, Vetiver, Spikenard, Sandalwood and Oud actually improve with age like wine. Five year old Patchouli demands a high premium and is eagerly sought after by natural perfumers. I’ve smelled Sandalwood that was allegedly over two hundred years old and it was the best I had ever encountered. There are countless anecdotes circulating of 100 year old Rose oil and 100 year old Frankincense oil and 50 year old Cedar Wood oil, all just as good, if not better, than when they were first distilled.
So, (1) cold pressed citrus oils will noticeably deteriorate after a year or so, (2) the majority of essential oils will remain stable for many years or many decades, and (3) others will get better and better as time goes by.
The concept of shelf life as it pertains to perishable products requiring preservation really does not apply to essential oils. So long as essential oils are properly stored in amber bottles, kept away from light and heat, and left tightly sealed, they will last indefinitely, and in some cases, will actually improve in quality as they age.
