Some essential oils are exactly what they say they are: a pure distillation or expression from their plants of origin. Some, however, contain water, alcohol, or solvents used in their extraction (see How are essential oils obtained from plants?). Others are mixed with other substances derived from plants to extend the batch, allowing bottlers to stretch their supply of an expensive essence without the high cost of obtaining more of it. Some are synthetic, laboratory-produced versions that smell the same as the natural ones or that contain just the fragrance component of the more complex oil—and, therefore, may not be the natural product that consumers have been led to believe they are.
Labels that claim that an oil is “100 percent pure” may be honest or not, as no governing body or agency regulates these oils or determines what “pure” means for them. The U.S. Food and Drug Administration (FDA) prevents essential oil proprietors from claiming that these oils have specific medicinal properties or that they can protect users from viruses or bacteria that cause diseases. Under FDA rules, substances that make these claims must be laboratory tested and peer reviewed and will then be examined by the FDA, classified as drugs if the research bears out, and be federally regulated. Very little research has been done to prove that essential oils—individually or collectively—can guard against or cure any illness, so labeling and advertising generally do not make these claims. More to the point, the FDA plays no role in determining the purity of these oils or in substantiating any other claims made by companies marketing the oils.
It may seem on the surface that consumers have no way to tell which oils are pure and which are not, but there are clues to help buyers decide which companies may offer a purer oil.
First, essential oils should be packaged in dark brown or green glass bottles to protect them from vaporizing in bright light. Companies that package their oils in less costly clear glass know that their oils are in no danger of vaporizing or otherwise altering their chemistry, probably because they contain something more than 100 percent pure essential oil.
Every bottle of essential oil should display the plant’s scientific or botanical name (in Latin) and the method used to extract it from the plant, as well as its point of origin—whether the crop from which this bottle was distilled came from lavender fields in New Mexico or the rosewood forests of Brazil. If the Latin name is missing, chances are that the content of the bottle is not strictly the essence of that plant. If there’s no point of origin or method of extraction, the oil might have been assembled in a factory instead of being hand expressed in a barn halfway around the world.
Essential oils should be priced according to the availability of the oil and the complexity of the extraction process. Scarcer oils are priced higher, and essential oil sellers pass on the cost to the consumer of higher-priced processing for oils that are more difficult to obtain. Purveyors of these oils who price them all identically—for example, hawkers at carnivals and festivals whose vials of oils are all the same size, shape, and price—may have some adulterated oils in their inventory. If their oils also come in clear glass bottles, the alert consumer can be certain that the content of these bottles is not entirely what it seems.
Even the most well-known and trusted essential oils marketing companies, however, can sell oils that are not as pure as their labeling suggests. The only way to be certain of what is in an essential oil is to order gas chromatography-mass spectrometry (GC-MS) laboratory testing, a costly step most consumers will not take. GC testing separates the molecules of various substances from a gaseous sample to allow them to be identified and studied independently of one another. Mass spectrometry captures these compounds as the GC instrument releases them and sorts them according to their mass in less than a second, making it possible to identify and analyze them. These tests can identify if an oil is truly from the plant it says it is, as well as particulars like the geographic location of a particular cultivar or the oil’s plant origin (such as the difference between lavender and lavandin, which come from the same family but have marked differences in scent, making one preferable to individual consumers over the other).
The process is not infallible, as many compounds are very similar and may be mistaken for one another, and some compounds in essential oils are still virtually unknown to modern science. Nonetheless, the analysis certainly will answer the question of whether or not the oil contains 100 percent of the compound(s) advertised or a number of different compounds that are not essential oils. GC-MS testing also identifies synthetic compounds in essential oils, making it particularly necessary and valuable for determining the oils’ purity for their use as preservatives in organic foods.