ANTIPERSPIRANT EFFICACY 443 antiperspirant ingredients, aluminum chlorohydrate,* at 3 different concentrations, ! 0, 15, and 20 per cent w/w, are summarized in Table I. These efficacy values were ob- tained from different test panels. Average point estimates were obtained by taking antilogarithms of the average of the logarithms at each concentration. Analysis of variance on logarithmically transformed data, in conjunction with a Neuman-Keuls range test, shows the following order of effectiveness at 95 per cent confidence limits: 15 per cent 20 per cent, and 10 per cent. No significant statistical difference in efficacy is observed between 10 and 20 per cent concentrations. Surprisingly, the efficacy reaches a maximum, rather than a plateau. Reasons for this occurrence are un- known. We have, however, observed similar trends with other basic aluminum "salts." Table I Per Cent Sweat Reduction for Aluminum Chlorohydrate a Concentration 10 Per Cent w/w 15 Per Cent w/w 20 Per Cent w/w Average 25 b 63 38 (11-38) ½ (57-68) (30-47) 38 56 35 (27-48) (43-69) (23-46) 36 58 50 (26-47) (50-67) (39-60) 43 44 (30-55) (38-51) 40 37 (30-49) (26-47) 51 (35-56) 46 (39-53) 39 • 59 40 aChlorhydrol. © bPoint estimate per cent sweat inhibition. ½Per cent confidence limits. •Antilogarithm of average logarithms at each concentration. Table II Per Cent Sweat Reduction for Aluminum Bromohydrate • Concentration Per Cent w/w Per Cent Sweat Reduction 95 Per Cent Confidence Limits 10 52 24 63 28 51 36 46 43 46 43-61 6O-66 46-56 38-54 39-53 aB.A.B.© *In our studies, we used Chlorhydrol ©, a product of Reheis Chemical Company, Division of Armour Phar- maceutical Company, Berkeley Heights, NJ 07922.

444 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS For example, an isolog of aluminum chlorohydrate is aluminum bromohydrate.* Efficacy data for this product are shown in Table II. Again, we observe a peaking effect. In this case, however, the maximum efficacy occurs at 24 per cent (5 per cent A1), whereas for aluminum chlorohydrate the maximum efficacy occurs at 15 per cent (3.75 per cent A1). While the analysis shows a maximum for dose-response data, we are not totally con- vinced that this peaking effect is real. To help resolve this problem, we plan to run multiple crossover studies with aluminum chlorohydrate at several different concentra- tions. ALCOHOL SOLUBLE ANTIPERSPIRANTS Since many new products on the market use anhydrous or hydroalcoholic vehicles rather than predominantly aqueous ones, we explored the effect of solvent on anti- perspirant activity. Most nonaqueous formulations use an aluminum chlorohydrate "type" complex alone or in conjunction with A1Cla. Since we already know the efficacy of aluminum chlorohydrate in aqueous systems at different concentrations (Table I), it would be instructive to compare the effectiveness of one of these systems with an analogous hydroalcoholic formulation. Table III shows the per cent sweat inhibition for a 50 per cent ethanol solution of aluminum chlorohydrate at 20 per cent to be 41 per cent. The alcohol has not attenuated the activity of this product, as can be seen by comparing the above efficacy with that in Table I (39 per cent) for the same product at an identical concentration. We have observed similar results for A1-Zr combinations. While h•Ydroalcoholic systems are as efficacious as aqueous systems in the formulations studied, some reduction in activity for anhydrous systems has been noted. Table III Per Cent Sweat Reduction for Alcohol Soluble Antiperspirants Antiperspirant a Per Cent Sweat Reduction 95 Per Cent Confidence Limits Aluminum chlorohydrate b propylene glycol complex 21 9-31 Alcohol soluble ½ aluminum chlorohydrate 47 40-55 Aluminum chlorohydrate d 41 31-52 aAll solutions made up to 5 per cent A1 in SDA-39C. bRehydrol©, Reheis Chemical Company, Division of Armour Pharmaceutical Company, Berkeley Heights, N.J. 07922. cA.S.C.©, Reheis Chemical Company, Division of Armour Pharmaceutical Company, Berkeley Heights, N.J. 07922. d50 per cent hydroalcoholic solution. *B.A.B. ©, Reheis Chemical Company, Division of Armour Pharmaceutical Company, Berkeley Heights, NJ 07922.