The purity of essential oils comes into question fairly regularly. There is no hard-and-fast definition of “purity” in the industry; the generally accepted rule is that 100 percent of the oil must come from the plant of origin. This means that there should be no other adulterants in the bottle—that is, chemicals, water, or oils from other plants (unless the bottle contains a blend).
The top essential oils companies define their brand by the purity of their oils, with the understanding that if they added chemicals to their oils and consumers discovered this, it could lead to the end of their business. Some of these companies provide long descriptions of their testing processes on their websites as evidence that they take their commitment to purity seriously. At least one company—Rocky Mountain Oils—actually provides gas chromatography-mass spectrometry (GC-MS) test results for each of its oils on its website.
Gas chromatography separates different kinds of molecules in an essential oil to find any that are different, sending all these downstream to the mass spectrometer. The spectrometer then captures the molecules, ionizes them, and breaks them down into bits to make it possible to identify substances that should and should not be in the oil. Ionization makes these particles of matter detectable by a device called an electron multiplier. This process must be carried out in a science laboratory by trained professionals, and most essential oils companies who test their own oils before bottling engage with a third-party lab for greater impartiality and integrity.
In the end, it comes down to trusting a particular brand and its statements about the integrity of their essential oils. No governing body supervises the purity of essential oils, so any company that sells them can claim that they are 100 percent pure without having to define what this means, prove their purity, or even test the oils to be sure that the claim is true.
One of the ways purveyors of essential oils can make the case for their products’ purity is through chain of supply (or supply chain authentication), a tracking process that requires everyone who handles the oils—from the farmers who sow the seeds and harvest the plants to the processors who distill or press the oils from those plants, and on to the bottling operation—to follow a set of strict rules, to ensure that the oils are not adulterated. If there are gaps in the process—if the oils are diverted to a place that is not part of the established chain, for example—the chain of supply is broken, and the oils would have to undergo rigorous testing to be sure that they have not been contaminated or changed in some way.
Companies that maintain an unbroken chain of supply often advertise this on their websites to emphasize their commitment to purity and quality. Young Living, for example, calls the process its Seed to Seal program, requiring trusted suppliers to follow specific protocols for growing and handling the oils it sells. doTerra’s description of its CPTG purity testing process (see What is a “therapeutic grade” or a “food grade” essential oil?) also fits the definition of a chain of supply, with the added step of rigorous testing at each step.
Adulteration of oils is a common practice for some companies that offer oils at budget prices. Most consumers are not likely to send their oils to laboratories for GC-MS testing to see if they contain chemicals other than the plant essence, so these companies often get away with selling these oils as “pure” when they are not. If you are considering buying discounted oils from an online seller, keep in mind that what you are buying may contain synthetic chemicals that dilute the potency of the oil while stretching a batch to fill more bottles.
Additionally, improper storage of essential oils can damage them, affecting their strength, scent, and value to the consumer. These oils should be packaged in dark amber glass bottles, so an oil in a clear bottle may suffer damage caused by ultraviolet rays, especially if the bottles are stored in the path of direct sunlight. Companies that sell oils at a discount sometimes bottle them in clear glass vials, a sure sign that they may not be worth whatever money you may save by purchasing them. Look for dark glass stored in a cool, dry place, well shielded from sunlight or broad-spectrum lighting that may include UV rays.