j. Soc. Cosmet. Chem., 44, 65-67 (January/February 1993) Letters to the Editor TO THE EDITOR: The article entitled "Comparison of exaggerated and normal use techniques for assessing the mildness of personal cleansers" by B. H. Keswick et al. (J. Soc. Cosmet. Chem., 43, 187-193, 1992) purports to demonstrate superior predictive ability and relevance of an arm wash protocol compared to a flex wash protocol. There are several pieces of data presented in the Keswick article that are contradicted by published data as well as being internally inconsistent. The lack of specific experimental details, such as the number of subjects, inclusion criteria, and description of grading scale(s) make comparison with the literature even more difficult. These deficiencies call into question the validity, not only of the conclusions, but of the actual data as well. In a previously published study by Sharko et al. (1), two products with very similar formulations to products A and B described in the Keswick article were tested using an arm wash test. In the Sharko article, well-established instrumental assessment tech- niques were used in addition to the standard expert clinical evaluation such as that reported in the Keswick article. The product A analogue was significantly (p 0.05) less irritating than the product B analogue and caused significantly less damage to the barrier as assessed by TEWL. There were directional differences (0.05 p 0.1) showing product B to cause a greater increase in blood flow when assessed by a Periflux Laser Doppler Velocimeter and greater redness when measured with a Minolta Chro- mameter. These results are self-supportive and consistent with our own flex wash tests and the flex wash reported in the Keswick article. However, in the Keswick article, the authors claim that their arm wash test actually had results opposite to those reported in the two flex wash tests and the arm wash test mentioned above. We have conducted dozens of flex wash tests as well as less aggressive arm wash and face wash tests over many years, and have never observed such a cross-over. The data from the in home-use test with the product pair reported in the Keswick article adds no value since there were no significant differences observed, except for a claimed significance for a very small difference in leg dryness. Even in this case, if any appro- priate nonparametric analysis of the data were conducted, it is unlikely that the small difference reported on legs would be significant. Since there is no question that the flex wash is the more aggressive procedure, it is quite surprising to observe that for products A, C, and D in the Keswick article, the "milder" arm wash protocol produced markedly greater erythema than the flex wash. This finding 65

66 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS is also not consistent with information already in the literature regarding clinical testing of surfactants (2). Finally, the results of the appliance test reported in the Keswick article are very con- fusing and again inconsistent with the arm wash data presented in the same article. Although the product used was not identified, it may be inferred from the erythema score that the product is similar in irritation potential to product B. However, when using the towel, no irritation was observed--a lesser insult than that produced by the "milder" arm wash methodology. Keswick et al. do not attempt to explain these glaring inconsistencies. The description given of their consumer use model certainly cannot account for such inexplicable differences. In summary, the results of the study of Keswick et al. do not support any known models of surfactant-induced irritation, and the proposed model for irritation produced in a flex wash is simplistic and inaccurate. Not only are the data internally inconsistent, but they are contradicted by published information. These major discrepancies must be ad- dressed. REFERENCES (1) P. T. Sharko et al., Arm wash with instrumental evaluation--A sensitive technique for differentiating the irritation potential of personal washing products. J. Dermatol. Clin. Eval. $oc., 2, 19-27 (1991). (2) P. J. Frosch, "Irritancy of Soaps and Detergent Bars, in Principles of Cosmetics for the Dermatologist, P. Frost and S. N. Horwitz, Eds. (C.V. Mosby Co., St. Louis, 1982), pp. 5-12. Richard I. Murahata Unilever Research U.S. Gary L. Grove KGL, Inc. TO THE EDITOR: This responds to comments made regarding our article, "Comparison of exaggerated and normal use techniques for assessing the mildness of personal cleansers," which recently appeared in your journal. Specifically, this addresses criticisms that the article provided insufficient experimental detail and that the results presented are inconsistent. As we noted in our article, the forearm and flex wash methods examined were based on methods previously published in this journal (1,2), and the procedural details requested are available in the cited works. Neither the reviewers nor the editor deemed it necessary to repeat these details in our article. For those who may not have read the original articles, the forearm and flex wash studies were graded on seven-point and four-point scales, respectively. The forearm wash studies used 30-40 subjects for each product comparison, the flex wash implement study used 13 subjects for each treatment com- parison, and the flex wash studies used 40 subjects for each product comparison. These sample sizes met or exceeded the sample sizes specified in the original papers. The home-use studies were scored using the same grading scales as the forearm wash studies, with between 80 and 90 subjects randomly assigned to use each test product.