By: Retha Nesmith, Certified Aromatherapist
I recently read a post about whether or not essential oils expire. In the post I read, the author stated that pure essential oils do not expire. They said that essential oils don’t grow mold, mildew or yeast because they do not contain water and have antiviral and antibacterial properties. All of this information is true. What the author left out is how outside properties can indeed affect essential oils. Proper storage is imperative.
There have been many studies done on this subject. It turns out that there are three main things that can change an essential oil. But before we talk about those things I just want to make sure everyone knows exactly what an essential oil is. An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. These volatile aroma compounds are chemical constituents that make up the essential oil. These chemical constituents are the therapeutic properties of the oil. For example, Peppermint is very high in the chemical menthol. Menthol has a ‘cooling effect’. It also has analgesic properties or pain relieving properties. If Peppermint didn’t have menthol in it then it no longer would be one of the top oils for reducing fevers and relieving discomfort.
So what are these three outside forces that can change essential oils? They are oxygen, heat and light.
Oxygen! “oxygen can change the chemical composition of an essential oil by reacting with some of the constituents.”-Essential Oil Safety. If oxygen is changing the chemical composition of an essential oil, then we no longer know what chemicals are in that oil unless the oil gets another test. Just like the example I gave with Peppermint, some oils might no longer be good for what they were originally good for. This oil maybe hasn’t “expired” but we might want to be aware of this so we don’t continue to use it for a purpose that won’t do any good. One study showed that the “monoterpene content of Lemon essential oil decreased from 97.1% to 30.7% in 12 months when the oil was stored at 77 degrees F with the cap removed for three minutes every day. However, storage at 41 degrees F, with the cap removed for three minutes once a month results in minimal degradation.”- Essential Oil Safety. So Lemon had not expired because it was still a great oil, just a completely different oil then what it was probably originally purchased for.
Heat! Not enough research has been done on heat causing degradation as much as oxygen. However, there have been a few studies showing that extreme heat can change the chemical make up of an essential oil.
Light! “Light will promote the formation of oxygen free radicals, which are highly reactive.” One study done on Orange Sweet shows that when it was exposed to UV light at 68 degrees F for 50 minutes it’s composition changed dramatically. Multiple chemicals increased, many chemicals decreased and there were even 12 NEW chemical constituents found within the oil.
Maybe essential oils don’t “expire” but they should have a shelf life. This is to make sure you are getting the most out of your essential oils. Maybe they don’t mold or grow mildew but they do change. If you are not aware of these extreme changes and store the essential oils incorrectly, then you might be using an oil that is not what you really think it is.
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