Checking the expiration dates on food is obviously the safe approach.
But it’s probably going too far to throw out staples or personal care products that could survive a nuclear holocaust, just because they’re a few days past their printed expiration date.
For some products, however, the issue isn’t as clear-cut.
Pure essential oils, for example, don’t contain water, and they have innate antiviral and/or antibacterial properties. These traits mean they’re not going to grow mold, yeast or mildew over the long-term.
But is there any chance they could eventually go bad anyway?
Let’s find out.
Essential Oils Aren’t All The Same
That gallon of milk that you bought at the convenience store? Its shelf life is going to be much shorter than the organic milk you usually get at Whole Foods. That’s because quality matters.
Similarly, many products sold as essential oils are of questionable quality and can’t be legitimately compared to pure essential oils sold by companies like Public Goods. Some of those lesser products are pure oils that have been mixed with cheaper oils from nuts or seeds, so the vendor can sell more of them.
Other bargain oils aren’t pure plant extracts at all. They’re not distilled or pressed from plants, but are simply synthetic oils made to smell like their legitimate counterpart.
All these “fake” pure essential oils have going for them is their price. They aren’t going to deliver the anticipated results when used in aromatherapy, and they’re more likely to spoil quickly.
There’s another “X factor” involved, even when using high-quality, pure essential oils. They’re almost always diluted with carrier oils, because using essential oils can irritate your skin due to their strength. Some carrier oils like black currant and borage have the shortest shelf life and can go bad after just six months, and commonly-used ones like grapeseed and soybean oil typically last just a year. Coconut and jojoba oils, on the other hand, can last more than five years.
So the moral of the story is: don’t just judge the quality of your essential oils by looking at the label to check the oil’s GC/MS numbers (gas chromatography and mass spectrometry, which measure the oil’s chemical composition). The shelf life of essential oils also depends on what’s used as a carrier oil.
What Causes Essential Oils to Lose Effectiveness?
We’ve already mentioned that pure essential oils aren’t vulnerable to many of the usual culprits — yeast, mildew and mold — that often cause products to spoil or become rancid. Sealed essential oil bottles kept in a dark, cool place can theoretically last almost forever.
Problems start to develop, however, when the oils are exposed to outside elements.
The therapeutic properties and benefits of essential oils are largely based on the active ingredients in them. The most important ones are monoterpenols, sesquiterpenes, monoterpenes, sesquiterpenoids and monoterpenoids, and the latter two will oxidize when exposed to the air.
Just as oxygen steals electrons from iron and causes it to rust over time, oxygen saps electrons from these key essential oil ingredients and changes their chemical composition. This transformation doesn’t necessarily mean that the oils will become rancid or spoiled, but they won’t provide the benefits that you buy them for.
Light and Heat
Light, particularly sunlight, can quickly cause changes in the chemical makeup of essential oils. This effect happens because a short period of exposure to UV light causes the formation of oxygen-free radicals in the oils, altering the composition of their chemicals and even forming some brand new ones. There’s also some evidence that exposure to high heat can change the chemical balance and makeup of essential oils.
How do you know if your essential oils have oxidized? Some, particularly limonene-containing citrus oils like lemon and grapefruit, will smell bad. Others, like peppermint and chamomile, will change color; still others may have a noticeable change in their viscosity.
In all of these cases, the benefits of the essential oils when they’re applied to your skin or put into a diffuser are degraded or lost. After that deterioration, the products are only beneficial for some skincare applications.
A few oils like tea tree and lavender, however, can actually irritate mucous membranes or the skin, or cause sensitization, if used after they’ve oxidized.
These factors make it crucial to store pure essential oils in a cool, dark place.
Proper Storage of Essential Oils
These guidelines are used by the manufacturers of pure essential oils, but are just as important to keep in mind if you’re a DIY’er who makes your oils at home, or if you simply buy them off the shelf and want to make sure they last as long as possible.
- Use dark-colored glass bottles to prevent UV light from penetrating the container; essential oils can degrade plastic bottles
- Refrigerate the bottles to prevent heat-cause oxidation (aniseed, fennel and rose otto may solidify in colder temperatures but won’t be damaged)
- Keep the bottles tightly capped and stored carefully, and follow essential oil safety guidelines like keeping them away from heat and flames
How Long Do Essential Oils Last Under Optimal Conditions?
The answer is different for different oils, because they all have different chemical compositions. Most will last at least two years before starting to degrade, unless they contain one of the unstable carrier oils mentioned earlier. And some can last for as long as 15 years without losing their effectiveness.
Many experts advise replacing essential oils every three years to be safe. The exceptions are patchouli, ylang ylang, vetiver and sandalwood because they actually improve as they age. But three years is on the short end of the lifespan scale for some other essentials.
Here’s a categorized list of the essential oil shelf life you can expect, as long as they’re treated and stored properly.
For those who want to learn more about the longevity and benefits of essential oils, we recommend books written by aromatherapy expert Robert Tisserand. If you’re not sure whether your essential oil has gone bad, the best idea is to consult your own aromatherapist, who can show you the telltale signs to look for.
And the best way to ensure you get the highest-quality essential oils is to buy them from a reputable provider like Public Goods, which takes great care in properly producing, bottling and storing every bottle of essential oil it sells.
The highest quality for the lowest cost.
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