The toxicity of essential oils

Abstract

Rasooli et al. have reported the anti-listerial effects of thyme oil.1Rasooli I. Rezaei M.B. Allameli A. Ultrastructural studies on antimicrobial efficacy of thyme essential oils on Listeria monocytogenes.Int J Infect Dis. 2006; 10: 236-241Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar The authors state that “essential oils such as thyme oils (…) could be considered as preservative materials on some kinds of foods (…) they could find an application as additives to foodstuffs (…)”. Essential oils, including those from different species of thyme, have a variable composition of components, some of which are acutely toxic to humans in small amounts. Eugenol, which is a component of thyme oil from Thymus capitatus, cilicus, funkii, and vulgaris, is hepatotoxic.2James S.E. Price C.S. Thomas D. Essential oil poisoning: N-acetylcysteine for eugenol-induced hepatic failure and analysis of a national database.Eur J Pediatr. 2005; 164: 520-522Crossref PubMed Scopus (46) Google Scholar, 3Dr. Duke's phytochemical and ethnobotanical databases. USDA, ARS, National Genetic Resources Program. Phytochemical and ethnobotanical databases. National Germplasm Resources Laboratory, Beltsville, Maryland; 2005.Google Scholar In children, as little as 10 ml of eugenol-containing clove oil has led to near fatal hepatic failure.4Hartnoll G. Moore D. Douek D. Near fatal ingestion of oil of cloves.Arch Dis Child. 1993; 69: 392-393Crossref PubMed Scopus (40) Google Scholar Other toxic effects of essential oils include mucosal irritation, vomiting, epigastric pain, diarrhea, convulsions, renal failure,5Riordan M. Rylance G. Berry K. Poisoning in children 4: household products, plants, and mushrooms.Arch Dis Child. 2002; 87: 403-406Crossref PubMed Scopus (29) Google Scholar and central nervous system depression.6Lane B.W. Ellenhorn M.J. Hulbert T.V. McCarron M. Clove oil ingestion in an infant.Hum Exp Toxicol. 1991; 10: 291-294Crossref PubMed Scopus (32) Google Scholar Chronic toxicity has also been described: terpineol, which is a component of thyme oil from Thymus eriocalyx, is mutagenic in the Salmonella/microsomal assay (Ames test).7Gomes-Carneiro M.R. Felzenszwalb I. Paumgartten F.J. Mutagenicity testing (+/−)-camphor, 1,8-cineole, citral, citronellal, (−)-menthol and terpineol with the Salmonella/microsome assay.Mutat Res. 1998; 416: 129-136Crossref PubMed Scopus (143) Google Scholar Linalool, which is a component of oil from the same Thymus species, has been shown to be cytotoxic to human skin cells.8Prashar A. Locke I.C. Evans C.S. Cytotoxicity of lavender oil and its major components to human skin cells.Cell Prolif. 2004; 37: 221-229Crossref PubMed Scopus (157) Google Scholar Essential oils, including thyme oil, can therefore not be recommended for use in food preservation. Like any artificial food additive, every component would need to be tested rigorously for toxicity before its contact with food for human consumption could be permitted. Conflict of interest: No conflict of interest to declare.