A laboratory and literature based evaluation of allergic contact dermatitis to fragrance chemicals

Allergic contact dermatitis (ACD) is an immune response to specific chemicals called allergens. Many fragrance chemicals are presumed to be allergens based on dermatologist case study and anecdotal reports. Because of this, legislation has been passed in the European Union to identify and target potential allergens in attempts to lessen the risk to sensitive consumers. This legislation, the 7th Amendment to the Cosmetics Directive, was enacted by the Scientific Committee on Cosmetic Products and Non-food Products (SCCNFP), a European legislative body that oversees the regulations surrounding cosmetic products. This legislation is largely a labeling directive to inform consumers if certain fragrance materials present in consumer products exceed specified limits. There is much debate between dermatologists, regulators and the cosmetics industry as to whether the legislation is based on sound scientific research. The legislation has raised many questions including should there be limits for these 26 materials, if so, how should they be set, and most importantly the basic question, are these fragrance materials allergenic? The purpose of my project was to contribute research that would address each of these questions using a three-point approach via two laboratory-based experiments and a literature review. The first experiment focused on characterizing the chemistry of two fragrance materials; geraniol and citronellol, in terms of their volatility and effects of such volatility on dose. Accurate dose estimation is a key factor in performing reliable patch testing, the method used by industry for testing of fragrance materials for allergenicity. Results showed that both materials were volatile and lost a percentage of the doses applied, thereby lessening the dose that would be available when testing. The second experiment used in vitro diffusion cell methods to determine the skin penetration potentials of the same two fragrance chemicals. Penetration through the stratum corneum and epidermis is required to elicit a skin sensitization response. Experiments showed both materials had low skin penetration which greatly affects their abilities to induce allergenicity. The third section of my research employed a semi-quantitative scoring method using a weight-of-evidence approach to review the body of literature existing on another fragrance material; farnesol. This methodology served to review all the available data and identify existing data gaps to get an accurate overall summary of the strength of evidence showing farnesol was a fragrance allergen. My review showed the available studies do not document a clear causative determination that farnesol is a contact allergen.;Altogether my three areas of focus demonstrated that there is not a strong body of evidence pointing to the existence of strong skin sensitization potentials for geraniol, citronellol or farnesol.