Shelf Life and Storage of Essential oils
Some facts about Essential Oils: They are volatile natural chemical compounds that are susceptible to changes in the environment in which they are stored. They react and change composition in the presence of light both natural and artificial, temperature, containers that the oils are stored in. Essential oils particularly the citrus oils and ones with a high terpene levels, herbaceous oils deteriorate very quickly in the presence of oxygen in the air, sunlight and higher ambient temperatures. The ideal conditions are to store oils under 20° C in dark glass bottles stored in a dark dry cupboard. Some precious oils can be stored in a domestic fridge at 5°, they may thicken but can be warmed in the palm of your hands to melt them ready for use.
Containers are really important too as they can impact the composition of the finished product. You need to ensure that whatever you store essential oils in they are the right vessel for the oil. The same goes for Vegetable carrier oils although there is more flexibility with carrier oils as they are more inert. Aromatherapists usually use coloured glass such as amber, blue, green or especially spray coloured to suit your branding. The darker the glass the better, and there is a violet/black glass that has the best light protection but they are expensive containers to consider. If the volume of oil stored is bigger, aluminium with a lacquer coating on the inside is the best up to about 10-15kgs after which lacquered metal drums should be used. Plastic is not to be used for long term storage of pure essentials oils as not only do they interact with the plastic material causing the container to bulge or retract, the interaction of the plastic with the chemicals of the oil can cause a change in the composition of the oil and small traces can be picked up in the oil.
Closures are important too, preferably tamper proof to protect against accidents with children. Normally essential oil bottles use closures that are fitted with integral droppers or restrictors to prevent the oil rushing out of the container. You can also use wadded screw caps that restrict the exposure of the oil to the air which contains oxygen and causes deterioration and oxidation of the oil. It is also worth remembering that in a large container, as the level goes down there is a greater volume of air above the oil and this leads to oxidation, evaporation and general deterioration of the oil. The best thing to do in this situation, is to decant the oil into smaller containers until it is finished.
The presence of light, sunlight or lightbulbs causes a speeding up of the deterioration of the oil, hence the use of dark coloured bottles. Artificial light contributes to deterioration at a slower rate but are still responsible for this. Always keep essential oils well away from naked flames, heating elements and any spillages must be cleaned up as they happen to prevent build up of the vaporised oil which can then lead to explosions. Essentials oils are highly flammable so make sure they are stored safely!
Taking all this in to consideration, bottled essential oils have differing shelf lives. Most will have a expiry date of 3 - 4 years, however check for expiry dates on the label or box. Citrus oils tend not to last as long, even when kept in the ideal conditions, normal shelf life being 12-18 months. It is always better with these oils to buy in smaller quantities and more often to keep them fresh. With carrier oils the same applies but carriers can oxidise quickly with odd odours, “chip fat” smells that relate to the oils rancidity. Generally, carrier oils last between 6-18 months providing they are stored in optimal conditions. The rule to follow is the guidelines that your suppliers give and to source and find professional suppliers. Do not compromise on quality when choosing your oils for your practice.