A volatile fragrance chemical that occurs naturally in cloves, basil, and bay leaves, among other plants. Its toxicity is similar to phenol, a potent irritant. Eugenol is often part of the fragrance in cosmetic products, and is known to cause irritation that may include redness, dryness, scaling, and swelling (Sources: Toxicological Sciences, October 2011, pages 501-510; Immunopharmacology and Immunotoxicology, July 2011, Epublication; Collegium Antropologicum, March 2011, pages 83-87; Toxicology In Vitro, August 2009, pages 789-796; and Toxicologic Pathology,August 2007, pages 693-701). It is a major component of clove oil, and research has shown the eugenol content of clove causes skin cell death, even when low concentrations of clove (0.33%) were applied to cultured skin cells (Source: Cell Proliferation, August 2006, pages 241–248). It is best to avoid products that contain eugenol, and it's definitely a fragrance ingredient to check on before buying cosmetics.