Farnesol
Also known as Farnesol, 3,7,11-Trimethyl-2,6,10-dodecatrien-1-ol, 2,6,10-Dodecatrien-1-ol, 3,7,11-trimethyl-, trans,trans-Farnesol
“EU SCCS says: restricted.”
Farnesol (CAS 4602-84-0) is an acyclic sesquiterpene alcohol (C15H26O; 3,7,11-Trimethyl-2,6,10-dodecatrien-1-ol) used as a fragrance ingredient with a delicate floral/lily-of-the-valley odor. It is one of the original 26 fragrance allergens listed in EU Cosmetics Regulation 1223/2009 Annex III (Reference 82), requiring label declaration above 0.001% in leave-on products and 0.01% in rinse-off products. The SCCS opinion SCCS/1459/11 (2012) classifies Farnesol in Table 13-1 as an established contact allergen in humans with rating ++ to +++ (between 11 and 1000 published positive patch-test cases) and additionally itemises it in Table 13-5 (Established fragrance contact allergens of special concern, single chemicals only) as one of 12 fragrance allergens posing a high risk of sensitisation to the consumer. NOTABLE: SCCS does NOT classify Farnesol as a prehapten or prohapten (absent from Table 13-6); the prehapten list comprises Geranial, Geraniol, Geranyl acetate, Limonene, Linalool, Linalyl acetate, and alpha-terpinene — Farnesol's sensitisation is intrinsic to the parent molecule rather than autoxidation- or bioactivation-mediated. The Schnuch et al. 2004 IVDK multi-centre patch-test study (Contact Dermatitis 50:117-21) found 1.1% (22/2021, 95% CI 0.7-1.6%) of consecutively-tested dermatitis patients positive to farnesol at 5% petrolatum, with strong association to propolis sensitivity (OR 6.2); the 2010 follow-up (PMID 20858058) confirmed clinical relevance of these reactions. The RIFM Fragrance Ingredient Safety Assessment (Api et al. 2023, Food Chem Toxicol 182 Suppl 1:114229) provides the most recent industry-derived safety evaluation. CIR has NOT published a standalone safety assessment of Farnesol — verified absent from the Dec 2017/Jul 2018 QRT (alphabetical traversal: Fibronectin → Formaldehyde with no Farnesol row between them, where it would belong); under CIR policy, fragrance-only ingredients are deferred to RIFM. Reg (EU) 2023/1545 expanded the Annex III allergen list to >80 substances but did not change Farnesol's Reference 82 thresholds.
Naturally occurring sesquiterpene alcohol; constituent of citronella, cyclamen, lemongrass, rose, musk, and balsam essential oils, providing a delicate floral/lily-of-the-valley fragrance note.
Functions both as perfuming agent and as a deodorant ingredient (CosIng functions: Deodorant, Perfuming) due to weak antimicrobial activity against axillary odour-causing bacteria.
RIFM has comprehensively assessed Farnesol (Api et al. 2023, Food Chem Toxicol 182 Suppl 1:114229) supporting safe fragrance use at typical concentrations subject to the SCCS-recommended general threshold for high-concern allergens.
Unlike Limonene/Linalool/Geraniol, Farnesol is NOT classified by SCCS as a prehapten — allergen risk does not amplify substantially with air-oxidation aging, simplifying formulation stability requirements.
- · Cross-reactivity / co-sensitisation pattern with propolis is clinically significant — propolis-sensitised patients should be considered for farnesol patch testing and vice versa.
- · Reg (EU) 2023/1545 expanded the Annex III fragrance allergen list to >80 substances; transition period for new products through July 2028.
Established contact allergen in humans per SCCS/1459/11 Table 13-1: classified ++ to +++ (between 11 and 1000 published positive patch test cases). Asterisked as identified in 1999 SCCNFP fragrance allergens opinion.
Itemised in SCCS Table 13-5 as one of 12 'Established fragrance contact allergens of special concern' (single chemicals only) posing a high risk of sensitisation to the consumer (>100 reported cases) — alongside Cinnamal, Cinnamyl Alcohol, Citral, Coumarin, Eugenol, Geraniol, Hydroxycitronellal, HICC, Isoeugenol, oxidised Limonene and oxidised Linalool.
Mandatory EU label disclosure (Annex III Reference 82) when concentration exceeds 0.001% leave-on or 0.01% rinse-off; ingredient cannot be hidden under generic 'Parfum/Fragrance' declaration above these thresholds.
IVDK multi-centre patch-test prevalence (Schnuch 2004, n=2021): 1.1% positive at 5% petrolatum (95% CI 0.7-1.6%); strongest co-reactivity with propolis (OR 6.2) and a 4.3-fold association with fragrance mix I positivity. Disproportionate impact in young women and office workers (hand and face most affected).
No standalone CIR safety assessment exists — verified absent from CIR Quick Reference Table (Dec 2017/Jul 2018) by alphabetical traversal (Fibronectin → Formaldehyde, no Farnesol). CIR defers fragrance-only ingredients to RIFM (Research Institute for Fragrance Materials).
SCCS/1459/11 — Opinion on Fragrance Allergens in Cosmetic Products (adopted 26-27 June 2012). FARNESOL CAS 4602-84-0 listed in Table 13-1…
“FARNESOL* 4602-84-0 ++ - +++”— sccs_o_073.pdf, p. 104 (Table 13-1: Established contact allergens in humans)
EU Regulation 1223/2009 Annex III (Restricted Substances) — Reference 82: 2,6,10-Dodecatrien-1-ol, 3,7,11-trimethyl- (INCI: Farnesol, CAS…
“The presence of the substance must be indicated in the list of ingredients referred to in Article 19(1)(g) when its concentration exceeds: 0,001 % in leave-on products 0,01 % in rinse-off products”— EU Reg 1223/2009 Annex III, Reference 82 (Farnesol / 2,6,10-Dodecatrien-1-ol, 3,7,11-trimethyl-), column (h)