Re: Aging of Essential Oils
:) There's a lot of factors involved.Yes, some oils get better with age, some oils have such a long "shelf life" that it doesn't really matter, and some should be relatively fresh (but not JUST distilled -- the best distillers won't ship some of their oils until they're a few weeks old -- Lavender and Helichrysum are examples.
SO, to answer your questions:
- Oils that get better with age: Sandalwood tops the list, as it will actually be more costly the older the 'vintage'. I've found other woods to improve with age: Palo Santo, and likely Rosewood, also perhaps Cedarwood, though I have not experienced one that I new was aged.
- Many heavier oils and resin oils also seem to improve with age: Patchouli, Vetiver, Frankincense (CO2 at least), Myrrh, likely Spikenard.
- Oils will evaporate if you leave the lid off. This isn't typically done to age an oil faster. You'll simply loose oil. A quality aged Patchouli or Sandalwood has just been stored away for some time (a year at least), but not in an open bottle or jar.
- The oils do not necessarily become more biochemically therapeutically more potent. They just seem to have nicer aromas. We have a large library here at the store, and a lot of cumulative knowledge. No one has said an aged sandalwood will be more effective at preventing skin cancer (just an example from the research on the oil). The oil MAY thicken, but that's not necessarily an improvement.
- There's generally groups of shelf lives, and always exceptions. Some should be within the last year's distillation: Lavender, Tea Tree, Neroli, ALL pressed citrus oils -- however, a very respected aromatherapist (writer and holder of a Ph.D.) said even these oils can last almost indefinitely if stored in a dark bottle, with as little air space in the bottle as possible, and kept in a cool location. Their seems to be debate about refrigeration, but it seems the latest school of thought is that this is perfectly fine, as long as that's your "storage" bottle, not your "working" bottle. Don't take it in and out of the cold frequently -- keep a bottle out that you work from, and occasionally refill that.
This is a GENERAL order of shelf lives, from shortest to longest, if simply kept in a bottle that's been opened, but with the cap on and kept out of light and heat:
- So, it would be a very long and complex list to discuss the shelf life of each oil. One of our projects is putting up more technical documentation about each oil, and this will appear there.
1 - Pressed citrus oils and Neroli: One year or less
2 - Florals (but not Helichrysum, for example -- "florals" with floral aromas"
3 - Herbal oils - there's a wide range, particularly if you include the spice oils. Cinnamon will last a long time, but Tea Tree has been shown to cause contact dermatitis if it's been left out and not stored properly after a year.
4 - There are some oils where age doesn't seem to affect them either way. Certainly Helichrysum (some say a 5 year shelf life) is an example.
5 - Then oils that improve aromatically with age (but there's no evidence, again, for changes in therapeutics, other than aromatically).
Whew! Bottom line is, there's only a few oils that are certain to improve aromatically with age: Sandalwood and Patchouli are the most well known. The way they are most commonly aged is just stored away for a long time. And with other oils, just be aware of your storage methods. Light, heat and air CAN degrade the therapeutic value of SOME oils (though there is very little data on this -- other than these oils seem to cause skin irritation for a small group of the population.
Hope this helps! Please let us know if we can clarify any of this