Allergic contact dermatitis caused by farnesol: clinical relevance.
BACKGROUND
The fragrance material farnesol is cited as an infrequent but important cause of allergic contact dermatitis (ACD). It is included in the fragrance mix II patch series and requires labeling in the European Union if it is used in a consumer product.


OBJECTIVE
To review the existing literature to determine the causative role of farnesol in clinical contact allergy.


METHODS
Survey of the literature on farnesol studies; predictive and clinical elicitation tests in case reports, reviews, and abstracts.


RESULTS
Predictive animal studies demonstrated in most cases that farnesol was a nonsensitizer. However, 2 local lymph node assays (LLNAs) indicated strong sensitization potential. Predictive human test data indicated a low potential, if any, for sensitization in human tests with farnesol at 10% or 12%. A few clinical reports indicated low-level allergy or questionable reactions to farnesol, with 5% being the most commonly used. There were also reports in which no reactions were seen.


CONCLUSIONS
Predictive testing on farnesol in animals shows conflicting results depending on the study methodology used. Human predictive patch-test data also had gaps that prevented it from being definitive in pointing to a causative relationship between farnesol and contact dermatitis. The real sensitizing potential of a material can best be determined by evaluating the clinical and epidemiological data so as to help resolve the conflicting animal and human predictive test data.


CONCLUSIONS
This literature and scoring exercise showed that predictive and clinical elicitation data do not document a clear causative determination that farnesol is a frequent contact allergen. Detailed clinical relevance and patient studies should clarify the clinical problem farnesol represents.
Gilpin
Sarah
S
Research & Development, Aveda Corporation, Blaine, Minnesota 55449, USA. gilp0004@tc.umn.edu
Maibach
Howard
H
D000485:Allergens / Q000009:adverse effects* / Q000145:classification / Q000276:immunology; D000818:Animals; D003257:Consumer Product Safety; D016206:Databases, Bibliographic; D017449:Dermatitis, Allergic Contact / Q000209:etiology* / Q000276:immunology; D005204:Farnesol / Q000009:adverse effects* / Q000145:classification / Q000276:immunology; D006801:Humans; D023441:Local Lymph Node Assay; D010328:Patch Tests; D010476:Perfume / Q000009:adverse effects* / Q000145:classification; D018675:Toxicity Tests
D000485:Allergens; D010476:Perfume; D005204:Farnesol