Essential Oils Safety

We thought it was important to share this from “Essential Oil Safety: A Guide for Health Care Professionals” by Robert Tisserand, Rodney Young –


• A typical essential oil is a complex mixture of some 20–200 organic compounds, the great majority being present at levels of less than 1%. If sufficiently potent, these may still be important either therapeutically or toxicologically. 

• Essential oils are moderately volatile and lipid -soluble, and have a very small degree of water solubility. 

• Essential oils are either distilled or, in the case of citrus oils, cold-pressed. Other forms of aromatic extract include concretes, absolutes, resinoids and CO2 extracts. 

• There is a degree of variation in the concentrations of constituents in essential oils from the same species of plant. This is due to factors such as the plant’s environment and growing conditions, harvesting and distillation techniques, or genetics. 

• Plants of the same species that generate essential oils with quite different constituent profiles are called chemotypes. Chemotypes are genetically determined. 

• Essential oils are not generally subject to microbial contamination. 

• Contaminants such as phthalate esters and biocides may be found in essential oils , and traces of solvents such as cyclohexane may be present in absolutes. 

• Essential oils are subject to adulteration, in which either odorous or non-odorous substances are added to increase volume and, therefore, profits. 

• Contaminants and adulterants are generally detectable by laboratory analysis, such as GC, MS and NMR spectroscopy. 

• Contamination or adulteration may increase toxicity.

• Some essential oils are very sensitive to the effects of light, heat, air and moisture. To avoid degradation, all essential oils should be stored away from direct sunlight in tightly stoppered dark glass bottles in a cool place such as a refrigerator.

 •The addition of antioxidants to essential oils prone to oxidation (or preparations containing them) is recommended. 

•Degradation can lead to increased hazards. The oxidation of some terpenes, for instance, makes them more likely to cause skin sensitization. 

•Most toxic effects of essential oils are attributable to known constituents. 

•Each essential oil constituent is composed of one or more functional groups attached to a hydrocarbon skeleton. It is the combined effects of these constituents that lend the oil characteristics such as odor, therapeutic properties and toxicity. 

•The types of compound found in essential oils include hydrocarbons, alcohols, phenols, aldehydes, ketones, esters, ethers, peroxides, lactones, carboxylic acids, furans, furanocoumarins and sulfur compounds. 

•Phenols are often irritants, aldehydes and sesquiterpene lactones may be skin sensitizers, some ethers are carcinogenic, and some bicyclic, monoterpenoid ketones are neurotoxic. 

•Isomers are compounds that have identical numbers and types of constituent atoms, but differ in the ways in which their atoms are arranged in the molecule. Structural isomers differ in the way that their atoms are connected together, while geometric and optical isomers have the same connections between atoms, but different arrangements of atoms in space. 


1. It is important, for reasons of clarity, to distinguish between the various types of oils and extracts, and not all of them are referred to as ‘essential oils’. Unfortunately, however, there is no single word to describe the whole family of aromatic extracts, especially since for many people the word ‘extract’connotes a material that is specifically not an essential oil.

 2. CO2 extracts are relatively new and little used, and consequently there is little or no toxicological data on them. However, they are used in aromatherapy, as are the even newer ‘phytols’. Both CO2 extracts and phytols (not to be confused with the constituent, phytol) more closely resemble the aromatic material as it occurs in the plant, than do essential oils, but they are both more costly. 

3. β-Eudesmol, and various wood essential oils, mitigate the toxic effects of organophosphorus pesticides (Chiou et al 1995; Li et al 2006). 


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