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.
Unfortunately it’s not so simple. Not only can essential oils go bad, using expired oils can also cause some unwanted side effects.
So, how long do essential oils last? What steps can you take to maximize their shelf life? Let’s find out.
The Shelf Life of Essential Oils Aren’t All The Same
That gallon of milk 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 the carrier oil it’s diluted with.
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 have an extensive shelf life.
Problems start to develop, however, when the oils are exposed to outside elements. These external elements can impact the therapeutic properties, scent and safety of the essential oils.
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 the oils will become rancid or spoiled, but they won’t provide the benefits 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.
For example, in a 2005 study, researchers found that the constituents of sweet fennel oil had completely altered from oxidation when placed under a light for two months. Another study involving Sweet Orange essential oil demonstrated that the oil underwent extreme changes after 50 minutes of exposure to UV light. In fact, 12 new chemical constituents were found in the oil after UV exposure.
There’s also some evidence that exposure to high heat can change the chemical balance and makeup of essential oils. While more research is needed to fully grasp the impact that heat has on the essential oils, most manufacturers typically recommend keeping them away from high temperatures or sunlight.
How to Tell if Essential Oils Have Gone Bad
How do you know if your essential oils have surpassed their shelf life? Some, particularly limonene-containing citrus oils like lemon and grapefruit, will have an unpleasant scent. But with most oils, the aroma of oxidation can be less noticeable.
In this case, there are other ways to examine whether oxygen has shortened the shelf life of your essential oil. Others, like peppermint and chamomile, will change color; still others may have a noticeable change in their viscosity.
In all of these cases, the therapeutic 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.
So, How Long Do Essential Oils Last?
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.
How to Store Your Essential Oils
No matter what type of essential oil you prefer, the key to extending the shelf life is proper storage conditions. Thankfully, it’s relatively easy to keep your oils in prime condition if you know how and where to put them.
When it comes to the bottle, you should use dark-colored glass bottles to prevent UV light from penetrating the container. Most store-bought essential oils come in a glass bottle with an amber-colored shade, which deflects UV light. Essential oils can degrade plastic bottles, so homemade oils should always be poured into a glass container.
Although the dark amber glass thwarts UV light, it’s important to keep the bottles away from sunlight. As we mentioned, heat can speed up the oxidation process. To optimize the shelf life of your essential oils, store the bottle in a dry and dark place.
You should also keep the bottles tightly capped and stored carefully to avoid oxidation and chemical evaporation. Always follow essential oil safety guidelines like keeping them away from heat and flames. And of course, if you have children in the vicinity, keep the oils stored out of reach!
Refrigerating the bottles can prevent heat-cause oxidation. While certain oils, such as aniseed, fennel and rose otto, may solidify in colder temperatures, they won’t be damaged. Remove them from the fridge around 12 hours before you plan on using the essential oils. If there are waxy particles floating around, give the bottle a quick shake.
Most of these guidelines are also used by the manufacturers of pure essential oils. However, they’re 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 extend their shelf life.
What’s the Risk of Using Expired Essential Oils?
Even if you think your essential oil has gone bad, you may be wondering whether there’s any actual risk in using it. When the chemical composition of essential oils are oxidized, it’s not just the aroma that changes.
In certain cases, spoiled essential oils can cause skin irritation, rashes, burns and other adverse effects. Tea tree oil and lavender oil, for instance, are known to cause irritation once they undergo oxidation.
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 — ensuring optimal health benefits and a shelf life you can count on.
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