Does Valerian Oil Go Bad? Shelf Life and Signs of Oxidation

Valerian oil does not go off the way milk does. It does not turn mouldy or sour in a day. What happens is slower and quieter: oxygen works on the oil a little at a time, and over the years the bottle you open is no longer quite the oil you bought. That is oxidation, and once you know what to look for it is easy to manage.

Valerian Root Essential Oil

Our own Valerian Root Essential Oil, in sizes from 0.5 oz to bulk.

From $31.99

Shop Now →

What oxidation actually is

An essential oil is a crowd of small aromatic molecules, and many of them react with oxygen in the air. The Tisserand Institute describes the result as oxides and peroxides, and says these products are slightly toxic and can raise the risk of skin reactions (Is my bottle of essential oil oxidized or no longer good to use?). A review by Turek and Stintzing says oils are prone to conversion and degradation, that oxidative and polymerization processes can cost an oil quality, and that temperature, light and oxygen availability matter most (Stability of Essential Oils: A Review).

So the villains are three things you can control: heat, light and air. Moisture is a fourth that the Tisserand pages mention for cloudiness. Time is the multiplier, because each of them works every day the bottle sits.

How long we expect a bottle to last

We say our valerian oil typically keeps 3 to 5 years unopened, stored tightly capped in a dark, cool cabinet away from pets. Think of that as a range for a sealed bottle kept well, and not as a promise for one that has been opened, warmed and left half-empty. The Tisserand Institute says most oils keep well for at least a year or two before oxidation becomes significant, and that shelf life varies with an oil's constituents rather than the brand. Valerian is a heavy root oil, so for an opened bottle we would plan around the shorter end and check it by nose.

Signs an old bottle has changed

Do not expect a dramatic event. Look for a few quiet shifts.

The smell has moved. The Tisserand Institute says the scent weakens and the freshness fades. Arctander, writing on valerian oil in the perfumery classic Perfume and Flavor Materials of Natural Origin, notes that ageing gives the oil an isovaleric acid odour, the sharp, sour side of valerian that is already part of the root's reputation. Our reasoning is that an aged bottle may smell harsher and flatter at once, with the balsamic sweetness thinned out.
It has thickened. The Tisserand page says very old oils can thicken and eventually solidify, though that takes years.
It looks cloudy. Cloudiness is usually moisture that has got into the bottle.
The cap and thread feel tacky. A sticky residue on the neck is our reasoning from the thickening point: evaporated and oxidised oil leaves a gummy film. Wipe the neck after each use.

Valerian makes the smell test harder than it is for most oils, because its fresh smell is already strong and divisive. Our nose guide describes the fresh scent, and the best habit is to write down your first impression the day you open it. A year later, compare against that note, and against any fresh bottle you can borrow, which is the comparison the Tisserand Institute recommends.

What to do with a bottle you doubt

Oxidised oils are the reason to be strict about skin. The Tisserand Institute says oxidation products raise the chance of a reaction, so a bottle that smells off, has thickened or looks cloudy is a bottle to retire from skin use. Our skin page covers dilution and patch tests for fresh oil, and even then we recommend starting at 0.5% to 2% in a carrier and stopping if irritation appears. Put the old bottle with household hazardous waste according to your local rules, rather than down the drain, and replace it with a fresh bottle.

Habits that slow it down

Cap it every time. The Tisserand Institute says to keep caps on and to keep oils out of direct sunlight. Our bottles are amber glass with a black cap, and a closed cabinet adds to that.
Cut the air. The Tisserand page says more air in the bottle means faster oxidation. If you buy a larger size, decant working amounts into smaller airtight bottles so the stock stays sealed and the small bottle stays nearly full. Our guide to storing valerian oil has the details, and valerian oil sizes will help you pick a bottle you will finish.
Keep it cool. The Tisserand Institute says refrigeration roughly doubles an oil's useful life. If you use a fridge, label the bottle clearly, keep it away from food, and let it come to room temperature before opening, which is our reasoning for keeping condensation out of it.
Date it. Write the date you opened it on the bottle. A year-old bottle and a five-year-old bottle look identical from outside.

Valerian is an oil people buy in small amounts and use in traces, so a little bottle can last a long time. Buying the smallest size that suits you and finishing it while the scent is at its best is the simplest storage plan of all.