162 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS factant systems. The results also suggest that the binding of isethionate surfactants with corneum proteins is even weaker than what was reported in our paper. However, as we have shown, compared to the displacement mechanism, the miceliar solubilization ef- fects play only a minimal role in ANS removal from the corneum by anionic surfactants. It is true that we have used TEA-Na laurate with 0.04 mole/1 of TEA in the system instead of pure TEA-laurate. The ANS displacement experiments and the surfactant binding experiments were carried out under identical conditions with TEA-Na laurate rather than pure TEA laurate. Thus, the comparisons in the paper are valid. Since TEA is present in significant amounts in these systems, we believe that the results are not likely to be very different from that of a pure TEA-laurate system. We are puzzled by the authors' comment on the effect of pH and their attempt to reanalyze our water treatment data using data from two different experiments. Note that while results for substrates such as skin or stratum corneum are self-consistent within a particular series, experiments carried out at different times with different samples may not agree with respect to absolute numbers. The trends that one can see will, however, be consistent. It is, therefore, not valid for the authors to pick and choose data from experiments done at two different times with corneum from two different skin sources for absolute values. We expect that the authors are well aware of the significant vari- ability that exists in different skin samples. We wish that it were not so, but unfortu- nately such variability is a fact of life. In all our comparisons we used the corneum or skin from the same donor. The enhanced removal by TEA-laurate was greater than what could be explained by pH effect alone. However, it is possible that the higher pH of the TEA bar by itself may also be detrimental to skin condition. It is interesting to note that the authors did not choose to mention the Zein dissolution results (Table III in our paper), which clearly indicate that TEA-laurate interacts much more strongly with proteins than does SLI. The authors' comment on our explanation of the mechanism of ANS binding to corneum protein and its displacement by anionic surfactant also reveals a lack of understanding of ligand-protein interaction. We did not say that electrostatic interactions were not important. We said that the hydrophobic interactions can overcome electrostatic repul- sions. Regarding the question of statistical analysis of the data, we did show the standard error for each set of data. In fact, the differences between TEA-laurate and SLI, and TEA- laurate-based soap and the SLI-based bar were significant, with a greater than 95% confidence (p 0.05) limit. We did not selectively disclose data and we are prepared to defend all our conclusions. It seems to us that there is a basic confusion in the authors' minds between deposition on skin and binding to corneum proteins. The focus of our work was to measure surfactant binding to protein and not deposition per se. Using three different techniques (fluorescence, direct corneum binding, and Zein dissolution), we showed that TEA- laurate binds more to proteins than does SLI. The authors have not provided any evidence that suggests otherwise. It is possible that washing with a TEA-laurate cleans- ing bar causes less overall deposition on the skin than washing with an isethionate bar, although the original study [Wortzman et al. inJ. Soc. Cosmet. Chem., 37, 89-97, (1986)] demonstrating that by means of a fluorescein probe was faulty. The latter aspect is discussed in a forthcoming paper in J. Soc. Cosmet. Chem. In any case, it is quite mis-

LETTERS TO THE EDITOR 163 leading to imply that any material left on the skin by a cleansing composition is detrimental to skin. The isethionate bar is, in fact, designed to deliver desirable skin benefit agents on skin during washing. There is extensive literature data relating sur- factant-induced damage to surfactants' ability to bind to corneum proteins. There is no credible evidence in the literature that suggests that deposition of beneficial agents from a cleansing product correlates with skin damage. Furthermore, spin resonance data (manuscript in preparation) carried out in our laboratory show that the TEA-laurate bar deposits rigid precipitate whereas the isethionate bar leaves a fluid lipid-like material on the skin. We are confident that the authors would be able to verify this by a more careful FTIR study. We reemphasize that it is not the quantity but the quality of deposit that is of relevance to skin condition. It depends on the nature of the material being deposited and its interactions with specific components in the corneum. S. Mukherjee M. Margosiak K. Ananthapadmanabhan K. Yu M. Aronson Unilever Research US