There are several variables that can affect the quality and quantity of a particular essential oil. The quality and intensity of essential oils vary due to the plant variety, time of harvest, soil condition, method of cultivation, and process of extraction. All these factors play a significant role in the end result. It is important to know the origin of the oils and the reputation of the company providing them. Beware of synthetic versions made possible by recent advances in chemistry. When a very high quality essential oil is used, less of it is needed to obtain the desired effect. Also, it is important to note that essential oils obtained from cold pressing and distillation methods often produce the highest quality oils for aromatherapy use. When using a cheaper, perhaps adulterated oil, you naturally increase your risk considerable. This is why dealing with reputable producers and distributors is important. As a consumer, you can insist that manufacturers assure that their oils are pure and 100% natural.
Some aromatherapy companies are now offering their services of essential oil testing to guarantee purity. This procedure is called gas chromatography and involves very expensive, highly technical measurement and computation equipment.
A highly trained chemist will be able to decipher whether or not the test sample is genuine or adulterated and with what, as well as where and even what time of year the oil was produced. Chemists have been able to duplicate some of the major chemical constituents in the laboratory. Only a portion of the whole essential oil is synthetically produced in this way. Many, if not all, aromatherapists believe the "whole" or entire essential oil in its natural form should be used to insure its greatest therapeutic value. Otherwise, one increases the risk of toxicity.