Variability and Quality of Essential Oils

The quality of  essential oils available on the market today is extremely variable. There doesn't exist strict regulations and quality control on essential oils imported and distributed, no regulations as to what a natural essential oil has to be.

More than 95% of the essential oils world-wide, are produced for the flavor, fragrance and toiletry industry. This industry is mainly interested in uniform batches of oil, less in differentiating between natural or synthetic constituents. Local merchants and diverse middlemen in the industry are often tempted to adulterate the oil in order to raise their profit or meet certain market demands. For detailed information about adulteration of essential oils see Tony Burfield's informative article at

Adulteration is done for example by mixing of the genuine oils with synthetic derivatives, or with other oils of lesser value. Essential oils like of the Lavender ssp, Eucalyptus and Rosemary are often industrially required to contain a certain stable percentage of a certain compound, and since natural essential oils vary in their composition due to seasonal variations, these oils are adjusted, rectified by adding the desired compound from a synthetic source. Usually what is added is the synthetic equivalent to an oils major compound- such as synthetic linalool and linalyl acetate to a lavender oil. Industry, for example, requires an Eucalyptus oil to contain at least 80% 1.8 cineole. So, what can a producer or merchant do, if this years large production for the world market only contains 78% or even less of this compound? Just discard the entire production, or... rectify the oil.

From the petroleum industry we get today all kinds of synthetic volatile compounds at very low prices. Examples are limonene, nerol, linalool, cineole used in manufacture of soaps, detergents, shampoos, to fragrance tissues, candies etc. To detect synthetic compounds in essential oils is quite difficult. A simple gas chromatogram discerns not between synthetic or natural linalool for example, here chiral separation of the compound is necessary. More about that further down.

There was an interesting report published on bergamot peel oils, where some 53 commercial oils were tested. All of them were labeled 100% natural. However, thorough analysis showed 37 of them to be adulterated (Chiral GC), one was even 100% synthetic (labeled as 100% pure natural essential oil). A simple GC doesn't provide any guarantee. In the case of these bergamot oils, synthetic linalool and its acetate had been added.

Many essential oils are produced in so-called third world countries because of low labor costs. The stills used are in most cases not quite adequate and efficient, just like there exists no control on the use of pesticides and herbicides on the crops.

Another report, investigated 110 different essential oils for the presence of chlorine pesticides. The authors say, that the paucity of reports on pesticide residues in published scientific literature is due exclusively to the fact that detection is difficult because the physical and chemical characteristics are very similar to those of essential oils and present an analytic method (Schilcher and Habenicht 1997).

Organochlorine pesticides (OP's) were unequivocally found in 72 of the 110 samples, i.e. around two thirds of all the samples analysed. In 64 of these the levels were considerably greater than those permitted by the German residue limit ordinance (RHmV 1994).

In 62 samples more than 1 OP was found, alpha- hexachlorocyclohexane, lindane, hexachlorobenzene, alpha-endosulfan, and p,p ' DDE being the most common. Especially noteworthy was the presence of technical hexachlorocyclohexane (HCH) in 66 oils, the permitted limit being exceeded in 56 cases, while one sample contained some 50 times the limit permitted for this substance...

Highly significant also the finding of DDT contamination found in 21 samples. Both DDT and technical HCH are long since prohibited products in many countries. There was a tendency to higher concentration of OP's in oils from developing countries and Eastern Europe. All this is interesting in relation to the fact that OP's are regarded cancerous and especially linked to breast cancer. In Israel, breast cancer rate has fallen by 8% since these pesticides have been prohibited many years ago..

The market today is filled with essential oils called simply thyme oil, lavender oil etc. There exist many different thyme and lavender species with each their characteristic chemical composition. All to often the exact botanical species is not indicated, or the plant part distilled, nor the original origin of the oil.

Essential oils from the same species but of different origin show remarkable variation in their chemical composition. Sometimes these differences are so striking, that we speak of a chemo-type. That is when the main component is different. For example in the oils of thymus we can have a linalool, a carvacrol or a thymol chemotype. Of course each one of them has different therapeutic properties. Also the ratio of the components towards each other can differ significantly. That is why an oil of one origin most likely differs from others of other origins.

Even if certain merchants offer to show the quality of their oil by presenting a GC, it is obvious from the above, and from our own analytic experience, that a GC alone does not in any way present a garanty for quality or especially natural origin of any essential oil.

From the above, we can see, that the purchase of essential oils- especially when used therapeutically as in aromatherapy, is mainly a matter of confidence and trust. The close co-operation and communication between producer, merchant and customer is of great importance, and actually the only guaranty we can have on the quality of essential oils.

We label all our oils with the exact botanical species name, place of collection, and the chemotype if necessary. In addition we have analysed most of our oils by gas chromatography (GC) and mass spectroscopy (MS) for chemical composition analysis.