Shelf Life & Storage
Who knows the EXACT shelf life for each oil?
There is SO much information out there about essential oil shelf life, and truly so many variables, that this is a really difficult-to-answer question "in a nutshell". Every oil is different, some change significantly over time, some virtually not at all. Some get better (both aromatically and therapeutically) and some don't age so well.
Here we are going to review what 'essential oil aging' actually is, how it happens, and what you can do about it to preserve (and in some cases improve) the aromatic and therapeutic properties of oils in your collection!
What is a Shelf-Life?
Yes, it may seem silly, but let's define this. A 'shelf life' is the duration an essential oil can be stored in a particular condition and not loose its best aromatic and therapeutic property. Essential oils (and CO2 extracts) are complex chemical mixtures. Some of these chemicals are subject to oxidation or degradation by other means. Sometimes this degradation can be good, resulting in a better smelling, potentially more effective essential oil. Other times these chemical changes result in rancidity of the oil, where the aroma is "off" and therapeutic properties are lost.
What are the forces that are responsible for essential oil aging?
Heat, Light, and Oxygen (or, much less, other chemical interactions that could create side reactions). Let's look at how each of these forces affect the chemicals present in essential oils.
For HEAT we need to think about these oils as molecules and compounds in a solution. All of these chemicals in our essential oils are susceptible to reactivity or evaporation. What an increase of temperature will allow these compounds to mingle with each other more freely due to molecular motion or collisions. Heat generally speed's up changes, good or bad, on a chemical level.
Think of it like this: why do we make tea in boiling water not ice water? The answer lies with the temperature and how this effects mixing and molecular motion. Ice water is not a good environment to extract tea because the molecules are not colliding with one another and therefore cannot react or change. With temperature in essential oils it's the same idea. The higher we go the more these constituents will move around and react with one another.
Next on the forces involved is LIGHT, and this force is a little bit more straight forward comparatively. This comes down to UV (Ultraviolet) radiation inducing photosensitive reactions (light induced reactivity). If something goes through this reaction pathway it can react in a way that could not be achieved thermally. In some ways this is much more unpredictable than temperature reactions, but will take a lot of exposure to direct UV light for any reaction to occur. Storing essential oils in a clear bottle near a window will absolutely cause undesired reactions of our beloved oils.
Finally let's look at OXYGEN and how it affects essential oils storage. The problem with oxygen (not only is it all around us, making up 21% of our atmosphere), it is great at starting reactions in our essential oils. These reactions can often lead to undesirable results. When you leave a fruit or an avocado out in the kitchen it is oxygen that adds the brown color and rancid smell that we experience. In many cases this invisible gas that surrounds us is the main culprit in the shelf life of an oil. This oxidation that occurs is also sped up whenever we increase the temperature of our oil. So, the bottom line is, to keep an oil stable, we do not want to expose it to heat, light or oxygen (but again, some oils DO get better, both aromatically and therapeutically with age...
Let's go over some general trends
Now let's look at some shelf life years by essential oil type (The major chemical families for each oil are on its product page in a table as shown to the right. The table also includes the primary constituents For a refresher on chemical families click here, and many primary constituents of essential oils are described here):
Monoterpene Rich Oils: 1-3 years (Citrus oils are closer to the 1 year and most other oils closer to 2-3 years.)
Monoterpenol Rich Oils: 2-4 years (Oils like Tea Tree that are rich with monoterpenes are closer to two years oils like Clove that contain a majority of monoterpenols are closer to 4 years.)
Sesquiterpene Rich Oils: 6-10 years (These oils could be anything like Patchouli, Sandalwood, Ginger, or Vetiver would qualify as oils that age well - they can get better beyond 10 years, it's just a very difficult test to do!)
This is a great way to understand the shelf life for any oil. What you can do is identify what type of chemical family best describes an oil and use these guidelines to predict a reasonable time line for shelf life. Each single individual oil page on our site tells you what its major chemical families are, and you can use these as a guide
What is happening chemically to your particular oil?
Let's hypothetically say that you did not follow any storage recommendations and you left a cold-pressed citrus oil out in a bottle by the window sill.
Exactly what is happening to your oil? A few things are going on here, first the temperature is driving away volatile components of the oil. This is how a majority of the aging will occur in most cases.
Basically, the oil will get closer to it's boiling point of the chemical compound and begin to become volatile and vaporize until it leaves the solution all together. In our lime oil example here we also have limonene which is a very sensitive to light.
This is going through an oxidation degradation pathway, which basically means it's degrading limonene % over time exposed. The amount of oxygen that is in this particular bottle can also lead to increased oxidation. More oxygen in your bottle means more collisions with limonene, and therefore an increase chance to go down the degradation pathway.
The Ideal Storage Conditions for 'Sensitive' or 'Delicate' Oils (which you should always do with citrus oils, and just to be safe, most other oils unless you know they get better with age!)
- Keep at low temperature...refrigeration if possible. Keep temperature of oil consistent (moving oils in and out of a fridge will only play around with these temperature dependent reactions and should be avoided.) So a "cool, dark place" may simply be best.
- As above, do keep in dark storage.
- If you have access to nitrogen capping (this is just a can of nitrogen to blow into the top of an essential oil bottle to displace the oxygen, this can be used (which we do at Ananada). This exchanges the reactive oxygen for reactive nitrogen which is inert.
NOTE: In some cases we found that oils get BETTER with these processes! We have a proprietary process that we carefully monitor as we are aging our oils to ensure that we don't over-oxidize or over-age our oils.