194 JOURNAL OF COSMETIC SCIENCE EVALUATING THE MILDNESS/IRRITATION POTENTIAL OF SURFACTANTS IN PERSONAL CARE PRODUCTS A! Gabbiane!!i, Robert Hi!iermeier, Martha Tate and Michael Prendergast Rhodia, Inc., Cranbury, NJ 08512 Surfactants and surfactant blends are used in virtually every aspect of modem cosmetic chemistry. Their use as wetting and spreadability additives, as emulsifiers for creams and lotions, and as active ingredients in hair care, skin care and oral care preparations are wide spread and well known. Exposure of the general public to these materials on a regular basis has therefore become virtually inevitable. As a consequence, surfactants and surfactant blends must elicit negligible levels of irritation and meet increasingly higher standards for product mildness. While surfactants are routinely subjected to a wide battery of safety and irritation assessments there has historically been a paucity of published studies on the.irritation potential of surfactants in humans. This presentation will focus on recent studies used to evaluate the irritation potential of several key surfactants that are currently of interest in the personal care arena. Case studies will be reviewed in which various instrumental, clinical and subjective evaluations were used to assess both the beneficial and adverse effects of these materials including the determination of mildness and irritation potential. Simple irritation (versus sensitization) is generally classified into two broad categories: irritation resulting from a single exposure and irritation resulting from multiple, repeated or extended exposures. As a result of the aversion to animal testing in recent years and the difficulties associated with the interpreting and correlating in-vitro techniques to human responses, clinical patch testing remains the most predictive and widely accepted technique used to characterize both types of irritation. Forty eight hour patch tests are used to assess irritation resulting from a single protracted exposure while 14 or 21 day cumulative patch testing is used to determine the effect of repeated and extended exposure. Specialized evaluation procedures such as the forearm flex wash or modified forearm flex wash have also become popular for the evaluation of irritation potential. Consequently, the 48 hour patch test was initially used to evaluate the irritation profile of Sodium Laureth Sulfate (SLES), Sodium Cocoamphoacetate (SCA) and combinations thereof. All surfactants and surfactant combinations were evaluated as 3.0% (w/w) aqueous solutions. Results indicated that the greatest irritation is elicited by the pure anionic surfactant SLES and that irritation potential decreases proportionally upon addition of the amphoteric surfactant SCA (Figs. I & 2). Evaluation of Derreal Irfitancy { B48 Hou'-, B 88 Hou'-,] Effect of SCA Addition On SLES Irritation o o 20 % SGA I-.-•...,.- .--e--.... I Fi,qure I Fi,qure 2

PREPRINTS OF THE 1998 ANNUAL SCIENTIFIC SEMINAR 195 Based on the results of the 48 hour patch test, a 14 day cumulative irritation study was initiated in order to develop a more comprehensive portfolio on surfactant irritation profiles in humans. The study was expanded to include: Sodium Lauryl Sulfate (SLS - as a positive control), SLES, the newer high pudty version of Sodium Cocoamphoacetate (SCA) and Potassium Mono Alkyl (C•2) Phosphate (MAPS). In addition to the subjective evaluation of irritation by professional clinicians, Corneometer and Chromameter measurements were used to respectively measure surfactant associated dryness and to instrumentally quantify and correlate reddening with clinical erythema scores. To insure that all materials were evaluated at equivalent levels each of the surfactants listed above was diluted with DI water to a concentration of 0.5% active material. Surfactant blends were prepared by mixing appropriate volumes of the diluted materials. For example, 100 ml of a 0.5% (w/w) surfactant solution containing 75% SCA dilution and 25% of SLES dilution was prepared by mixing 75 ml of 0.5% SCA with 25 ml of 0.5% SLES. In addition, the 0.5% stock dilution of each respective surfactant was used to determine the irritation potential of the pure unblended surfactants. Results of the 14 day cumulative irritation test indicated that in all cases the pure MAPS and Amphoteric surfactants elicited lower irritation profiles than the comparable surfactant/SLES combinations or the pure SLES sample. Irritancy responses (as determined by the Mean Cumulative Irritation Score) for the pure surfactants indicated that MAPS was the least irritating followed closely by Cocoamphoacetate while SLES and SLS were the most irritating. Irritancy responses for the pure surfactants were ranked as follows: Least Mild-SLS SLES SCA MAPS--Most Mild Mean Irritation Score-40.3 I 30.9 I 11.8 I 4.48 As in the original forty eight hour patch test, combinations of SLES with amphoteric concentrations above 25% were found to attenuate the irdtancy potential of SLES with irritancy reductions being roughly proportional to the level of added amphotedc. Irritancy potentials of the anionic:amphotedc combinations at a ratio of 3:1, were not different from those observed for pure SLES. Results obtained for Corneometer and Chromameter measurements were in general agreement with the subjective expert evaluations. Consequently, rankings for surfactant induced dryness and erythema were similar to those obtained for general irritation. In conclusion, results obtained by the 48 hour patch test for SCA / SLES were predictive of results generated by the 14 day cumulative irritation test. In addition, good agreement was found between the subjective and instrumental techniques. These findings confirm the mildness of MAPS and amphotedcs in human clinical studies and demonstrate their ability to enhance the mildness of mixed surfactant systems. Additional testing will be required to evaluate the irritation potential of other neat and mixed surfactant systems.