Sensitization methodology and primary prevention of the research institute for fragrance materials

The Research Institute for Fragrance Materials Inc. (RIFM) has approached sensitization studies with fragrance materials as primary prevention of sensitization in the healthy, normal population. Secondary prevention, or avoidance of elicitation, most often suggested by dermatologists for patients presenting with dermatitis, has not been part of its program effort. Historically, RIFM evaluated the sensitization potential of fragrance materials using the human maximization test method; no animal models were used. In general, petrolatum was used as the vehicle. This is a harsh procedure whose main use may provide a measure of the uppermost limits of sensitization. Treating skin with sodium lauryl sulfate may be problematic and finding a laboratory to conduct the study may also be difficult. In addition, using a human predictive test method for both hazard and safety assessments is not ideal. The current practice involves a hazard assessment using an animal model, followed by a safety assessment in a human repeated-insult patch test (HRIPT). The animal test method is used to identify the sensitization potential and a no-effect level. Following a review of the no-effect level and the maximum skin level, a safety assessment in humans can be conducted. RIFM also modified the original vehicle used in sensitization testing, since petrolatum presents two major difficulties: solubility and inconsistent effects on skin penetration. Since the greatest exposure to fragrance materials is considered to be from a cologne-type product, ethanol was chosen as a more realistic vehicle. Further modification resulted in combinations of ethanol and diethyl phthalate, due to diethyl phthalate's use in many perfume formulations as a solvent and fluidizer. Human testing should not be conducted as a hazard assessment. If conducted as a safety study, induction of sensitization should be a rare occurrence. Thus, follow-up studies are not meaningful since the number of sensitized volunteers would be low. However, following a series of the RIPTs with various concentrations of hydroxycitronellal, RIFM identified a group of 41 individuals who became sensitized. An extensive 3-phase use study, with 3 diagnostic patch tests and 4 whole-body dermatological examinations showed that most subjects were able to use a bar soap, a moisurizing lotion and cologne-type products with up to 1% hydroxycitronellal. In subjects where sensitization was induced by predictive testing, no serious recurring adverse dermatological conditions developed.