As soon as you open a new bottle or container of essential oils and it comes into contact with oxygen, a process called oxidation begins. The oxidation process involves the changes of oxygen bonds between cells into carbon bonds.

Dssential oils don’t spoil like food does, but they do change over time. Because it’s hard to determine what the oils have changed into, it’s also hard to determine whether or not they’re safe to use.

The bottom line is, don’t inhale expired essential oils or use them on your skin after they have expired.

Most essential oils have a shelf life, but this shelf life can vary according to the type of oil. These tables show the average shelf life of specific oils.

Citrus family: max 3 years 

Floral family: 3-5 years

Leafy family: 3-5 years

Rooty family: 3-5 years

- Among many, essential oils that can be kept 5 years or more are:

a) Black Pepper

b) Cedarwood

c) Clove Bud

d) Copaiba

e) Frankincense

f) Ginger

g) Patchouli

h) Rosewood

i) Turmeric

j) Rose

k) Sandalwood

l) Vetiver

Here are some tips for how to extend the shelf life of your essential oils.

Reduce exposure to oxygen

To prevent your essential oils from expiring early and to ensure they stay potent, minimize the amount of time the cap is off the bottle. The longer the bottle is uncapped, the more the oil is exposed to the oxygen in the air.

Also, be sure to place the cap back tightly on the bottle. If it’s not screwed on tightly, oxygen may still get into the bottle and begin the oxidation process.

Keep away from light and heat

The best place to store your essential oils is in a cool, dry place like a kitchen cabinet or your bathroom medicine cabinet. Keep your oils away from direct sunlight or any other direct heat and light sources.

It’s also best to buy or use dark-colored glass containers for your oils. The more opaque the glass, the more protection it offers against oxidation.

Use smaller containers to store your oils

Smaller containers will prevent oxygen from being trapped in the bottle when it’s opened. This will prevent oxidation from happening earlier than it should and will extend the life of your oils.

Once you’ve opened a bottle of an oil, you should keep track of how long you’ve had it. A handy way to do this is to take a marker and write the date that you opened it on the label.

Use the charts above for a quick reference for shelf life, and throw out the oil once it hits its expiration date.

If your oil isn’t dated, here are some other indications that it might be time to toss it:

• the smell of the oil has changed since you first opened the bottle

• the color has changed, or it has become cloudy

• the consistency is thicker or thinner than it was when you opened it

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. 

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.

Resource: Healthline