Have you ever heard someone say “our essential oils are so pure they don’t have a shelf life?” I have and unfortunately, this is not accurate information. So do essential oils have a shelf life?
You see, purity has nothing to do with shelf life. An essential oil’s shelf life is largely dependent on its chemistry. A few other factors that can play into the shelf life is how it is stored and also how much oxygen it is exposed to.
What is an essential oil?
To help explain how this works, let’s first look at the definition of what an essential oil actually is.
An essential oil is a plant based product obtained during steam distillation or cold pressing that is comprised of volatile components which are highly aromatic.
If you can’t remember the entire definition, just remember this: essential oils are comprised of volatile components.
These chemical constituents found in essential oils are referred to as volatile components due to their rate of evaporation.
The aroma you smell when you are first exposed to an essential oil is created during the evaporation that occurs when an essential oil is exposed to the air.
The Chemistry of Essential Oils
Many oils are classified by enthusiasts into a few groups like citruses, florals, woods, etc. Generally, we can say some citrus essential oils will have a shelf life of 1-2 years depending on their storage and exposure to oxygen.
Ultimately, the shelf life is determined by its chemistry. Some essential oils that are primarily comprised of monoterpenes tend to have a shorter shelf life, while others that are predominantly sesquiterpenes have a longer shelf life.
To make it easier for you to understand, think of the essential oils comprised mostly of constituents from the chemical family monoterpenes as being very light or more prone to react with oxygen. When you think of sesquiterpenes, it is easier to think of those as heavier or more stable. The stability sesquiterpene constituents have allows for them to be less prone to reacting with oxygen.
For example, "lighter" essential oils are those that have a significant amount of monoterpenes. Lemon essential oil has anywhere from 56.6% - 75% limonene. It also contains several other chemical constituents from the chemical family of monoterpenes that when added together make up about 90% of Lemon essential oil.
Oxygen = Oxidation
With so much of Lemon essential oil chemical components in one family, it carries a shorter life span when we consider its volatility and also higher potential for oxidation. Again, the volatility of essential oils refers to the reaction that occurs between the chemical constituents of essential oils and the air or the rate of evaporation.
While the synergy between all of the chemical constituents within an essential oil work well together, they do not do well with oxygen.
The interaction with oxygen causes oxidation in the essential oil(s). The more they are exposed to oxygen, the more oxidized they become and the shorter their life becomes.
Many experts and qualified aromatherapists recommend storing your essential oils in a properly sealed/closed container and in most cases a refrigerator. Robert Tisserand actually has a short article called "Lemon on the Rocks" that discusses why essential oils should be stored in a cold room/refrigerator. Basically, heat speeds up the process of oxidation and cold can slow it down.
Why You NEED to Know the Shelf Life
The concern for understanding and knowing the shelf life of an essential oil is important for several reasons. Essential oils can become skin irritants after once they start to oxidize. This is why many companies offer sales on essential oils that are soon to pass the shelf life date and why others will sell expired essential oils at reduced pricing for cleaning purposes.
Oxidation naturally occurs every time you open your bottle of essential oil. While the orifice reducers are designed to minimize the amount of oxygen exchange in an essential oil bottle, they do not prevent it completely. Once the process of oxidation starts, it cannot be stopped, so it is important to think about these things.
Think about these things for a moment and consider how many times you open your bottle of lemon essential oil. Do you refrigerate it? Do you make sure the cap is properly sealed/closed each time?
Being safe isn’t just about dilution. Learn everything you can about the essential oils you use -not just their potential therapeutic properties. Purity and quality do NOT define an essential oil’s shelf life!