Essential oils are a product of nature. Every natural product has a shelf life. They’re natural, liquid chemicals and their chemistry can get altered under certain conditions.
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.
When an oil comes into contact with oxygen, light, and heat, its composition begins to change. Over time, it starts to lose its strength and effectiveness. This is why most essential oils are sold in amber-colored bottles — the darker glass provides better protection against ultraviolet light.
Does this mean that essential oils spoil or “go bad?”
Essential 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.