Definition: Farnesol is a colorless, oily liquid with a delicate sweet odor. It is a sesquiterpene alcohol that naturally occurs in the oils of citronella, cyclamen, lemongrass, rose, musk, and balsam​.

Use in Cosmetics: In cosmetics and personal care products, Farnesol is used in the formulation of aftershave lotions, cleansing products, colognes, deodorants, eye lotions, face powders, foot powders, fragrances, hair care products, moisturizers, shaving products, and skin care products. Its primary function is as a fragrance ingredient​.

Other Names: Farnesol is also known by names such as Farnesyl alcohol, 3,7,11-Trimethyl-2,6,10-dodecatrien-1-ol, 3,7,11-Trimethyl-2,6,10-dodecatrienol, Stirrup-A/WF, Stirrup-CRW, Stirrup-H, Stirrup-HB, Stirrup-TPW, 3,7,11,-Trimethyldodeca-2,6,10-trien-1-ol, FCI 119a, NSC 60597, Trimethyl-2,6,10-dodecatriene-1-ol, (2E,6E)-3,7,11-Trimethyl-2,6,10-dodecatrien-1-ol, α-farnesol, β-farnesol, and 3,7,11-Trimethyl-2,6,10-dodecatrien-1-ol (farnesol)​​.

Skin Sensitivities: Farnesol has been identified as a potential sensitizer. This means it may cause an allergic reaction in some individuals, especially those with sensitive skin. The International Fragrance Association (IFRA) has established a standard that restricts the use of Farnesol in fragrances because of this potential for sensitization​.

Risk: The European Cosmetics Regulation requires manufacturers of cosmetics and personal care products to indicate the presence of certain "allergenic" substances in the list of ingredients if they are present above certain levels in the product. The presence of Farnesol must be indicated in the list of ingredients when its concentration exceeds: 0.001% in leave-on skin products and 0.01% in products that are rinsed off the skin​.

EU 26 List: Farnesol is included in the EU 26 list of fragrances that must be labeled separately on the product packaging because of its potential as an allergen. This is to alert consumers with super sensitive skin who may have a reaction to Farnesol, making it easier for them to avoid products containing this ingredient​.

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