Essential oils do not become rancid. They do however, over the course of time, become oxidized, which results in deterioration, and causes them to lose the inherent therapeutic properties that are beneficial to users. While not all essential oils will lose their aromatic properties, in fact a few mature with age, all essential oils are subject to oxidation and the loss of therapeutic value over a period of time. Citrus oils, for instance, will begin losing their aromatic properties, as well as their inherent therapeutic qualities, within 6 months. It is because of this that essential oils benefit greatly from proper handling and storage.
The majority of essential oils available on the market are packaged and sold in dark glass vials, or bottles. Amber glass bottles, as well as cobalt blue glass bottles, are the preferred methods of storing individual essential oils and blends. These type of bottles help keep sunlight out, and sunlight is the prime suspect for causing essential oils to deteriorate. Clear glass bottles, although readily available, are not recommended for storing essential oils. Clear glass does not possess the ability to keep sunlight out. While storing essential oils in clear glass will not harm the oils themselves, the clear glass will allow sunlight in, and enhance the process of deterioration. Plastic bottles will not suffice for essential oil storage. Essential oils that are certified pure will cause plastic, and many other petrochemical products, to deteriorate rapidly. This, in turn, will cause the essential oil being stored to become ruined in a very short period of time.
Wooden boxes are also available for the purpose of storing essential oils. These boxes are often made available by the manufacturer selling the essential oils; however, they are also readily available from a number of craft outlets and stores. These wooden boxes will serve to keep the essential oils further protected from the damaging rays of the sun, and make transporting the oils from one location to another easy to accomplish.
Refrain from storing essential oils in bottles that come equipped with a rubber topped dropper. The rubber portion of the dropper will become gummy and tacky if stored within the essential oil bottle. This will ultimately have the same adverse effect as storing essential oils in plastic bottles in that it will cause the oil itself to become useless.
Most aromatherapists recommend storing all essential oils and products in a refrigerated environment whenever possible. If this type of environment is not available, then the next highest recommendation comes in the form of storing all essential oils and products in a cool, dark place. Pantries, cupboards and cabinets are all acceptable spots for storing essential oils, provided they are not in an area that receives exposure to high temperatures.
Many of the essential oils sold on the market come with an orifice reducer embedded in the neck of the dark glass bottle. This device can be left in place when using essential oils. It will help deliver drops of essential oils when needed without causing excess spillage and waste. At times it may be necessary to disengage this device to provide a sample of an essential oil to another interested party. When removing this device do so with caution and care. Once finished, the orifice reducer can be pushed back into place and the top of the bottle screwed back in place.