164 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table VI Correlation Between Odor Score and Skin pH Correlation coefficient p Spearman X, axilla 1 0.019 0.0348 0.852 X, axilla 2 0.04 - 0.0289 0.876 Y, axilla 1 - 0. 3804 0.05 - 0.3557 0.055 Y, axilla 2 - 0. 3039 - 0.2964 0.110 Z, axilla 1 - 0.3307 - 0.3972 0.032 Z, axilla 2 - 0.289 - 0.3187 0.086 This might be due to competitive inhibition of the sensory receptors of the human nose (20). Concerning the question whether the addition of triethylcitrate to a perfumed deodorant is useful, it can be stated that within the present trial a significant odor reduction was never achieved. This might be due to the fact that in intertriginous areas the skin surface pH is markedly higher than the normal skin pH of about 5.5 (13). Therefore, it can be suggested that a slight reduction of the pH value even favors bacterial growth and odor production, while a more marked reduction (to about 5.5) might lead to the opposite. The present results seem to be contrary to those published by Osberghaus (12). With a statistical certainty of 99%, he showed a better performance of a deodorant containing 1% triethylcitrate as compared to a deodorant containing 0.16% triclosan. Triclosan, on the other hand, was superior in its efficacy as compared to a placebo with a statistical certainty of again 99%. Since in the USA other triethylcitrate-containing perfumed deodorants are also available (21), our results seem to be of general importance. In fact, for each new preparation the efficacy of triethylcitrate should be proved. Under no circumstances can it be deduced that the once-demonstrated efficacy (12) of triethylci- trate leads to a general improvement of every deodorant. In order to evaluate the test product used, we chose the single-tailed Wilcoxon test (Table IV). All of the three perfumers were able to detect an efficacy of the total deodorant compared to placebo. The difference was somewhat more marked than with the test product with and without perfume and might be due to the presence of both triethylcitrate and ethanol in the latter preparation. As triethylcitrate seems not to lead to a significant improvement of the present deodorant formula, we presume a high odor reduction potency of ethanol. SKIN SURFACE pH No correlation between the use of a triethylcitrate-containing deodorant and the pH change of the skin surface could be found. Neither in trial period Y (test product against test product without triethylcitrate) nor in period Z (test product against placebo) could statistically significant pH differences be found. BACTERIAL COUNT Only in trial period Z was there a statistically significant difference in the number of

EFFICACY OF DEODORANT COMPONENTS 165 CFU found. The statistical probability here is even greater than 99%. This effect is neither attributed to the perfume component (period X shows no difference) nor to triethylcitrate (period Y shows no difference). Therefore, the explanation for the reduced number of CFU in trial period Z seems to be in relation to the ethanolic component of the deodorant. ODOR STRENGTH AND BACTERIAL COUNT A close connection between the intensity of malodor and the number of CFU on the skin was not found, although a significant correlation coefficient was found with the data obtained from the chief perfumer, twice in different contexts (Table V). In the placebo- treated axilla (period Z, axilla 2), however, both parameters seemed to be more closely related in relative terms. This seems to confirm the conventional hypothesis on the development of body odor due to bacterial degradation of sweat (6). ODOR STRENGTH AND SKIN SURFACE pH Correlating odor strength and skin surface pH value, we found an interesting result. By using triethylcitrate, and therefore possibly lowering the skin pH, skin surface enzymes are said to show a reduced activity, which leads to a slower decomposition of sweat, horny cells, and sebum (12). In the present trial, however, in three of six instances (Table VI, column 5), an inverse result was found. In the trial periods Y and Z we were able to show that with higher pH values the odor intensity was significantly lower. A possible reason for this fact is the presence of an environment still favorable to bacterial growth, even at a moderately lower pH. With respect to the complex deodorant formula tested here, it is tempting to increase the triethylcitrate concentration in order to assure a decrease in the skin surface pH to a value close to 5.5. Fewer skin bacteria seem to have their growth optimized at this physiological skin surface pH value (14). ACKNOWLEDGMENTS The authors express their gratitude to Markus Ollert, M.D., Munich, for critical review of the manuscript, and to Gerhard Harem, Ph.D., Munich, for his statistical advice. REFERENCES (1) K. Laden, "Introduction and History of Antiperspirants and Deodorants," in Antiperspirants and Deodorants, K. Laden and C. B. Felger, Eds. (Marcel Dekker, New York, 1988), pp. 1-13. (2) I. K. Emery, Antiperspirants and deodorants, Cutis, 39, 531-532 (1987). (3) J. S. Strauss and A.M. Kligman, The bacteria responsible for apocrine odor, J. Invest. Dermatol., 27, 67-71 (1956). (4) A.M. Kligman and N. Shehadeh, Pubic apocrine glands and odor, Arch. Dermatol., 89, 461-463 (1964). (5) H. P. Fiedler, Mikrobiologische Probleme der Hautpflege unter besonderer Berficksichtigung der Desodorierung, ,4rztl. Kosmetol., 10, 50-56 (1980). (6) J. J. Leyden, "Bacteriology of the Human Axilla: Relationship to Axillary Odor," in Antiperspirants and Deodorants, K. Laden and C. B. Felger, Eds. (Marcel Dekker, New York, 1988), pp. 311-320.