Although essential oils do not become rancid, they do oxidize, deteriorate and lose their beneficial therapeutic properties over time. Oils such as the citrus oils will oxidize and begin to lose their aroma and therapeutic properties in as little as six months. Not all essential oils diminish in aromatic quality as time passes. The aroma of essential oils such as patchouli and sandalwood mature with age, however, Robert Tisserand explains that all essential oils oxidize and are subject to losing their therapeutic value in time. All essential oils benefit from proper storage and handling.
To avoid deterioration and protect the aromatic and therapeutic properties of your essential oils, store them in amber bottles. Dark glass such as amber helps to keep out deteriorating sunlight. It is best not to store essential oils in clear glass bottles. Clear glass bottles are not harmful to essential oils, but clear glass does not protect the oils from damaging sunlight. In comparison, you may have noticed that most bottled beer typically is packaged in amber (brown) glass bottles to help protect the contents from exposure to light. Except for certain situations that most often pertain for bulk oil purchases, avoid purchasing or storing pure essential oils in plastic bottles as the essential oil will eat at the plastic, and the essential oil will become ruined over a short period of time. Some vendors sell oils in lined aluminum bottles. It has been said that aluminum bottles are acceptable if the interior of the bottles are lined.
Essential oils should also be stored in a cool, dark place.
Avoid purchasing essential oils that are stored in bottles that have a rubber dropper incorporated into its screw-top cap. Droppers with rubber bulbs should not be kept with the essential oil bottle as the highly concentrated oil can turn the rubber bulb into gum and ruin the essential oil.
Instead of a rubber dropper top, many essential oils that are sold to consumers in sizes of 1/2 ounce (15ml) and smaller are packaged in bottles that contain an orifice reducer. An orifice reducer is a small, clear insert inside the bottle opening that acts as a built-in dropper. Unlike the material that rubber dropper bulbs are made of, orifice reducers are made of a material that can withstand exposure to essential oils. The name orifice reducer may seem a little strange at first, but it’s a handy little dispensing device. You simply tip the bottle and you can dispense the oil drop by drop.