EVALUATION OF METHODS FOR MEASUREMENT OF ANTIPERSPIRANCY 249 methods have been used to collect the perspiration. Wooding, Jass and Ugelow (24), described a procedure in which the sweat was absorbed by silica gel contained in a capsule. Sweat produced on the enclosed area of the skin was measured by an increase in weight of the silica gel. A similar method was described by Randall and McClure (25), except that anhydrous calcium chloride replaced the silica gel. Variations of this method have been used by Kuno (4) and others (26). A capsule was attached to the skin, and dry gas passed through it. The gas stream was then passed through U-tubes where the moisture was absorbed either by anhydrous calcium chloride, phosphorous pentoxide (4) or a saturated solution of a suitable salt (26). The usual arrangement was such that the absorbing tubes could be changed quickly, and therefore measure- ments could be taken over short consecutive periods of time without too much manipulation of the apparatus. The gravimetric method for the evaluation of antiperspirants which has gained much popularity was described by Fredell and Read (27) and Fredell and Longfellow (28). They measured the amount of sweat secreted by the axilla by absorbing it onto tared gauze pads (Fig. 3). This method has been used to measure sweating and evaluate antiperspirants both during thermal stimulation and, over longer periods, during the normal working day. The procedure normally adopted is to compare the quantity of sweat produced by the right and left axillae before and after treatment of one axilla with an antiperspirant. Although the quantity of sweat produced by the axillae may differ, depending on temperature, humidity, stress, etc. the Weighing Weighing Figure 3. A diagrammatic representation of the axillary gravimetric method of measurement of sweating.

250 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ratio of the weights produced by the right and left side remains constant (27), provided both are untreated. A control ratio is determined, and then the antiperspirant applied to one axilla. The ratio is again measured, and the effectiveness of the antiperspirant can be determined from the change in ratios. The full method of calculating the results and the statistical analysis has been discussed by Wooding (30) and Daley (29). Other sites than the axilla have been used for gravimetric determinations (31). These sites do not produce as large a volume of perspiration as the axillae, and therefore the errors involved in measuring such small quantities tend to make these methods unsatisfactory. Although the gravimetric methods have found much favour, because of their simplicity and the ease with which numerical data for statistical analy- sis can be obtained, they too are not wholly satisfactory. The basis of the method is the assumption that the right to left ratio of sweat output is a constant (27). Under ideal conditions this may well be so, but under con- ditions encountered in laboratory tests this is not always so. The factors which affect sweating have been discussed both by Kuno (4) and by Reller (46), who have shown that certain stimuli such as posture, pressure, etc. can affect sweating unilaterally. A subject who has to spend several 1 h sessions in a hot room with pads under his arms does not remain perfectly still. Any movement can affect the relative sweat output from each axilla. The effect of leaning on one arm or the other is shown for one subject in Table I. It can be seen that the change in axillary R/L ratio can be so large as to obscure most antiperspirant effects if the subject leans one way, or make the effect look much better than it really is if the subject leans the other way. Table I The effects of posture on axillary sweating Sweat collected (mg) Ratio Right axilla Left axilla R/L 188 169 1.15a 222 155 1.36a 586 278 2.10b 260 237 1.10a 254 610 0.41½ 281 180 1.56a 290 195 1.49a a, Subject sitting upright b, subject leaning to the left c, subject leaning to the right.