Do essential oils expire? How long they last and how to tell
Do essential oils expire? Not in the way milk does. A pure essential oil contains no water, so mould and bacteria have nothing to live on, and an old bottle will not upset your stomach the way old food can (no essential oil should be swallowed anyway). But essential oils do age. Air, light and warmth slowly change the chemistry inside the bottle, and that matters for two reasons: the scent goes flat or harsh, and some aged oils are far more likely to irritate skin or set off an allergy than they were when fresh. So in practice every bottle has a useful life, and for skin use that life is shorter than most people assume.
Every spring I clear out my oil cupboard, and every spring I find at least one forgotten bottle, usually a citrus, usually smelling more of a paint shop than a fruit bowl. Here is what is going on in those bottles, and how long each kind of oil really lasts.
What happens to an essential oil as it ages?
Three things, mostly.
The first is oxidation. Some of the molecules in an oil react with the oxygen in the air sitting above it in the bottle, and every time you open the cap, fresh air goes in. The quickest to react are monoterpenes, the light, bright-smelling molecules that dominate citrus oils (limonene) and pine and resin oils (pinene). Linalool, the main component of lavender, oxidises too. As they react, they form peroxides and related compounds that are much stronger skin sensitisers than the fresh oil.
The second is evaporation. The lightest, freshest-smelling molecules escape first, so a bottle that is opened often loses its top notes and is left smelling heavier and flatter. Some oils thicken as this happens.
The third is the speed of both. Heat and light make everything happen faster, which is why a bottle on a sunny windowsill or a bathroom shelf ages far more quickly than one in a cool cupboard.
Not every oil ages badly. A few heavy oils from woods and roots, such as patchouli, vetiver and sandalwood, change very slowly, and perfumers say some of them round out with age.
Why does an old oil matter for skin?
Sensitisation means your immune system learns to treat a substance as an enemy. Once that has happened it usually lasts, and you may then react to the same compounds wherever you meet them: in perfumes, shampoos, washing-up liquid. Oxidised tea tree oil and oxidised lavender are well-known causes of allergic rashes, and dermatology clinics in Europe include oxidised limonene and linalool in their patch tests because so many people react to them. I go into the lavender side of this in what the research shows about lavender.
The practical point: an oil that smelled lovely and suited your skin three years ago is not the same oil today.
A note: links to Amazon here are affiliate links. As an Amazon Associate I earn from qualifying purchases.
A small help with this: amber dropper bottles, 30 ml on Amazon. A few more ideas sit at the end of this note.
How long do essential oils last?
These are rules of thumb that turn up across aromatherapy safety writing. They assume the bottle is opened now and then, capped tightly and kept somewhere cool and dark. Treat them as the outer limit for skin use, not a target.
| Type of oil | Examples | Once opened, use on skin within about | What ageing looks like |
|---|---|---|---|
| Citrus peel oils | Sweet orange, lemon, grapefruit, mandarin, bergamot, yuzu | 1 year | Flat, sharp or turpentine-like smell; may turn cloudy |
| Pine, needle and resin oils | Pine, fir, cypress, juniper berry, frankincense | 1 to 2 years | Harsh, paint-like note; sticky ring round the neck |
| Tea tree | Tea tree | 1 to 2 years | Harsher, more medicinal smell; skin itch after use |
| Most herb, leaf and flower oils | Lavender, peppermint, eucalyptus, rosemary, geranium, clary sage | 2 to 3 years | Top notes fade; a sour or vinegary edge |
| Heavy woods and roots | Sandalwood, vetiver, patchouli, Atlas cedarwood | Several years | Slowly thickens and darkens; often still pleasant |
| Your own blends in carrier oil | Any | A few months | Smell of old crayons or putty: the carrier has gone rancid |
Unopened bottles kept sealed, cool and dark last longer, but not for ever, because there is already a little air above the oil. A bottle bought on holiday and left in a drawer for three years before you open it has been ageing all that time, just more slowly.
Blends follow their weakest ingredient, which is usually the carrier. Jojoba, which is really a liquid wax, keeps for two years or more. Sweet almond lasts about a year once opened, and rosehip seed oil only about six months, even in the fridge. A face oil made with rosehip will turn long before the lavender in it does.
Do the dates on the bottle mean anything?
They help, but storage matters more. Some bottles carry a best-before date, a distillation date, or a small open-jar symbol with a number such as 12M, meaning 12 months after opening. Others carry only a batch number, which a good supplier can use to tell you when the oil was made. Many oils sold in Japan are classed as zakka (general household goods) and carry no date at all.
A lemon oil kept in a cool cupboard for 18 months may be in better shape than one left on a sunny windowsill for six, whatever the label says. So write the date you open each bottle on the label or on a strip of masking tape. It takes ten seconds and saves all the guessing later.
How can I tell if an essential oil has gone off?
Use your nose first, but not straight from the bottle, where everything smells strong. Put one drop on a paper tissue or a blotter strip, wait a minute and compare it with what you remember of the fresh oil. Signs of age:
- A sour, sharp, rancid or turpentine-like smell, or simply no brightness left.
- Cloudiness in an oil that used to be clear.
- A sticky or gummy ring round the neck of the bottle and the dropper insert.
- An oil that has become noticeably thicker or darker.
- A blend that used to suit your skin and now stings or itches.
Some changes are harmless. Rose otto turns cloudy or solid when it is cool and clears again in a warm hand. A few oils, such as vetiver, are naturally dark and thick from the start. If you are not sure, the rule is simple: keep it off your skin.
What should I do with old essential oils?
Do not put them on skin, in a bath or in a child's room, and do not lean over them for a steam inhalation. An oil that has turned has nothing left to offer your skin or your lungs.
A drop or two on a cotton pad tucked into the bottom of the kitchen bin, or into the getabako (the shoe cupboard by the front door), uses up an old bottle where nobody is breathing it closely or touching it. Keep the pad out of reach of children and pets, who will happily chew one.
To get rid of a bottle, soak up what is left in newspaper or kitchen paper and put it out with burnable rubbish, the same way many Japanese households deal with used cooking oil, rather than pouring it down the sink. Then sort the empty glass according to your local rules.
How to store essential oils so they last
- Keep them in dark glass, amber or cobalt blue, with the dropper insert in the neck and the cap screwed down after every use. Clear glass lets in light, and many plastics do not stand up to neat oil.
- Store bottles upright in a cool, dark cupboard, away from the stove, the bath, sunny windows and the top of the fridge, which is warmer than it looks.
- In a Japanese summer, a closed-up flat can get very hot during the day. If you have no cool cupboard, citrus oils can go in the fridge in a lidded box, well away from food and out of reach of children. Let the bottle come to room temperature before opening it, so moisture does not condense inside.
- Buy small. A 5 or 10 ml bottle of an oil you use now and then is better than a large one you finish four years later. Citrus oils in particular are worth buying in the smallest size you can find.
- Do not leave a rubber-bulb pipette standing in a bottle of neat oil. The oil perishes the rubber, and bits of it can end up in the oil.
- Label everything: the oil, the date opened, and for blends, the oils, the percentage and the date mixed.
For your own blends, a set of 30 ml amber glass dropper bottles on Amazon is useful, because the pipette suits a face or body oil that you will use up within a few months. Neat oils kept for longer are better in their original bottle with its screw cap and dropper insert. If you mix blends, the dilution calculator gives the number of drops for any bottle size, which makes it easy to mix only what you will use while the carrier is fresh. The essential oil dictionary also notes which oils oxidise fastest.
Is an old oil a reason to see a doctor?
Usually not, but a reaction to one can be. If any oil, old or new, gives you a rash, stop using it and wash the area with mild soap and water. See a pharmacist or doctor if the rash spreads, blisters or weeps, if it is on your face, or if it has not settled within a few days. If you have reacted to an oil once, or you have eczema, ask your doctor about proper patch testing at a dermatology clinic before you go back to using oils on your skin, because an allergy can make you react to everyday products too.
Fresh oils matter most for the people with the most sensitive skin: babies and young children, older relatives and anyone who is pregnant. Children and pets are no safer around an old bottle than a new one, so keep every bottle capped and locked away. If someone swallows an essential oil, phone a doctor or poison advice line straight away and do not try to make them vomit. Swelling of the lips, face or throat, wheezing or trouble breathing after using any oil needs urgent help: call 119 in Japan, or your local emergency number.
A five-minute cupboard check
Once or twice a year, take every bottle out and go through it:
- Is the opening date written on it? If not, guess honestly and write it now.
- Is it past its time in the table above? Retire it from skin use.
- Does it smell right on a tissue? If not, retire it, whatever the date.
- Is the cap tight and the dropper insert in place?
- Is the cupboard still cool, dark and out of reach of children?
Buy small, date every bottle, keep it cool and dark, and when an oil smells wrong, believe your nose.
The writer
Philippa is a British writer who has lived in Japan for many years and has blended essential oils at home for two decades. She looks after the Aroma corner and never writes a recipe without the dilution.
