When essential oils enter the bloodstream, they have an effect on the whole body. Essential oils can enter the bloodstream through various application methods (1). The oils circulate through the bloodstream and interact with tissues and cells throughout the body.

Eventually the circulating oils must pass through the liver, which is an organ situated in the lower-right side of the thorax, below the ribcage. The liver is thought to be the primary site of essential oil metabolism within the body. Metabolism is a term that refers to the life-sustaining chemical reactions occurring within living cells that provide for growth, reproduction, resiliency, and response to the environment. When the essential oil moves into the liver, specialized enzymes work to break down individual compounds into metabolites. These metabolites continue to circulate within the body before being eliminated, primarily in urine (2). Some essential oil metabolites may also be eliminated in the feces, through the skin, or exhaled from the lungs (3).

Many essential oil metabolites have been found to be biologically active and contribute their own favorable effects. For example, one study explored how limonene, the primary constituent in many citrus oils, is changed by the body to produce perillic acid as its primary metabolite (4). Although limonene itself is highly efficacious, perillic acid mimics the effects of limonene and can even demonstrate a stronger effect (5-7).

Another example is linalyl acetate, which is present in high amounts in lavender, clary sage, and bergamot essential oils. Enzymes in the body metabolize linalyl acetate to linalool (3,8). Linalool is thought to promote relaxation in the body (9). Interestingly, there is evidence suggesting that when linalyl acetate is administered by itself, it can also promote relaxation (10). Presumably this occurs because linalyl acetate is converted to linalool.

Essential oil metabolism is an exhaustively researched subject (3). Understanding how the body metabolizes essential oils helps users to better appreciate their wellness-promoting power.

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Jager W. Metabolism of terpenoids in animal models and humans. In: Baser KHC, Buchbauer G, eds. Handbook of Essential Oils: Science, Technology, and Applications.Boca Raton, FL: CRC Press. Taylor & Francis Group; 2010:209-234.
Chow HHS, Salazar D, Hakim I a. Cancer Epidemiol Biomarkers Prev. 2002;11(November):1472-1476.
Zhang Z, Chen H, Chan KK, Budd T, Ganapathi R. J Chromatogr B Biomed Sci Appl. 1999;728:85-95.
Gelb MH, Tamanoi F, Yokoyama K, Ghomashchi F, Esson K, Gould MN. Cancer Lett.1995;91:169-175.
Fukumoto S, Sawasaki E, Okuyama S, Miyake Y, Yokogoshi H. Nutr Neurosci. 2011;9(April 2006):73-80.
Bickers D, Calow P, Greim H, et al. Food Chem Toxicol. 2003;41(7):919-942.
Kang P, Seol GH. J Pharm Pharmacol.2015;67(5):714-719.
Koto R, Imamura M, Watanabe C, et al. J Cardiovasc Pharmacol. 2006;48(1):850-856.

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