As a quick reference...
What you shouldn't do:
What you can do:
For more details and how to know if an oil has 'gone bad', keep reading!
We get this question quite often, and while it’s not an easy answer, I don’t recommend just throwing out old or expired essential oils. There may still be some uses for them which you may not have considered. If you do want to dispose of them, it should be done properly.
One of the first indicators may be the aroma. Many citrus oils which are expeller pressed from the peel or “camphoraceous” oils such as ti-tree will develop an unpleasant smell. Knowing what a fresh oil smells like will help you compare. Remember to always pour out a small amount of the oil onto a paper or tissue to evaluate. Oil residue around the top of the bottle will oxidize as it is exposed to air and interfere with the content in the bottle.
If you have stored your oils in areas of direct sunlight, extreme hot and cold (e.g. in a car), left lids off for extended times, then your oils may suffer from premature degradation.
You may have remembered approximately when you bought the oils which may be a significant time of a few years or more has passed, or if there is an expiry date it could be an indicator. However, shelf life of essential oils is not a rudimentary period of time as they are all quite different.
For example, essential oils high in monoterpenes and oxides will have a shorter shelf life while oils rich in esters, aldehydes or phenols will last for many years. Some resinous oils, absolutes or from roots may improve with age such as vetiver.
The oils to be most concerned with are ones high in mono-terpenes and oxides. Most of these would be considered “top” notes or essences. When these chemicals oxidize, they can emit an unpleasant smell (which is a good indicator) and cause more irritation to the skin. They will also lose therapeutic potency such as antibacterial properties.
These would include all citrus oils expeller pressed from the peel such as lemon, orange, bergamot, grapefruit, tangerine. Other volatile top note oils would include ti-tree, eucalyptus globulus, cajeput, rosemary & pine. If you suspect any of these oils have gone off, any therapeutic use in topical solutions or diffusion is not recommended. However, they will be useful for killing weeds and sprinkling around areas outside where pests are a problem. You could also add them to soaps for cleaning as they will provide better degreasing and dirt dissolving activity.
I do not recommend putting these oils down the drain as the pipes in many newer homes are made of ABS or other plastic material which can be degraded by these chemicals. If you have a septic system, a sudden influx of a large amount of essential oil can upset the delicate balance even though the oil is natural.
On to some of the oils to be considered “middle notes” such as lavender, juniper, peppermint, lemongrass, basil. Many of these will have significant alcohols which will start to degrade reducing typical antiviral properties. The oil may become thicker with a sticky residue forming around the top. The aroma can also change although it may not be as unpleasant as when terpenes go off. Once again, topical therapeutic uses are not recommended but they can still be used in cleaning soaps, room sprays and in the case of basil and lemongrass, some outdoor bug repellency. You may want to saturate some cloths or pieces of wood around your outdoor living area.
And, pleeeaasse do not respond back to tell us your oils wont oxidize or go “off” because they are organic, therapeutic grade, best in the world, blessed by some patron saint no one has ever heard of or from a sacred, energetically aligned region of earth. That is just nonsense. Everything degrades at some point, and essential oils being volatile chemical elements are not exempt.
In fact, the more “natural” many things are, the faster it will generally happen. Even if you have the best quality essential oils, storage also plays a significant role but that is a whole other article to investigate
For further reading, check out our blog: Essential Oils - A Day in the (Shelf) Life