ENVIRONMENTAL PARAMETERS ON SWEAT GLAND ACTIVITY 251 data are provided in Table I to demonstrate the effects of environmental conditions on axillae sweating. For all of the studies described in this section, two subjects were chosen to undergo a rigorous series of tests. Reported values represent an average of two measurements con- ducted on different days. While this may seem like a small sampling pool, we found the results to be extremely reproducible when all environmental parameters were carefully controlled. As indicated in Table I, increasing the RH increases the rate of perspiration in both subjects. Likewise, we observe a similar effect for an increase in temperature. Data are shown for 30% RH and temperatures of 37, 45, and 52ºC. This humidity may be eas- ily attained at all three temperatures. However, when we try to go to higher humidity Figure 3. In Test 2, subjects were placed in the sauna chamber with absorbent pads in the axillae region, which were weighed for a period of 45 min in increments of 5 min. Table I Perspiration Rates (g/min) Calculated from Plots of Perspiration vs. Time for Various Temperature and Humidity Settings in the Sauna Chamber Subject 1 Subject 2 Left Right Left Right 30% RH, 37°C 0.0414 ± 0.006 0.0406 ± 0.003 0.0189 ± 0.006 0.0149 ± 0.004 80% RH, 37°C 0.0848 ± 0.002 0.0893 ± 0.007 0.0377 ± 0.000 0.0357 ± 0.000 30% RH, 45°C 0.0790 ± 0.001 0.0848 ± 0.005 0.0405 ± 0.002 0.0295 ± 0.002 60% RH, 45°C 0.1212 ± 0.058 0.1238 ± 0.055 0.0757 ± 0.001 0.0661 ± 0.004 30% RH, 52°C 0.1384 ± 0.009 0.1391 ± 0.007 0.1044 ± 0.006 0.0927 ± 0.003

JOURNAL OF COSMETIC SCIENCE 252 levels, such as 80% RH, we are limited to lower temperatures (37ºC) due to dewpoint constraints. At 45ºC we were limited to 60% RH, and at 52ºC it was very diffi cult to exceed 35% RH. In any event, we observed changes in perspiration output as a result of temperature and humidity variation. For example, increasing the humidity from 30% RH to 60% RH at 37ºC results in an increase in perspiration activity. Increasing humidity results in two principal outcomes. First, the effi ciency of evaporative cooling decreases since high levels of humidity in the air permits less evaporation of sweat on the surface. As a result, sweat remaining on the surface increases in temperature and acts as an insulator to the external environment, thereby making it more diffi cult for body temperature regulation. Second, an increase in humidity, while keeping the tem- perature constant, results in an increase in the heat index, which is a parameter designed to predict the effective temperature as perceived by humans. At both temperatures, we observe an increase in axillae perspiration when the humidity is increased from 30% RH to 60% RH and 80% RH. When the humidity is held constant at 30% RH and the temperature is increased from 37ºC to 45ºC and 52ºC, we also observe an increase in axillary activity. In the FDA monograph guidelines for antiperspirant testing, the hot room conditions are specifi ed at ~38ºC (100ºF) and 35–40% RH. Further, subjects are allowed to acclimatize for 40 min followed by two 20-min periods of sweat collection. While the tests com- pleted in this study do not precisely follow this protocol, our fi ndings are very useful in illustrating the temperature and humidity effects on sudoriferous behavior. They also show the importance of dewpoint temperature as a major factor that should be consid- ered. Dewpoint is defi ned as the temperature to which air must be cooled in order for water condensation to take place. The higher the RH, the more the dewpoint tempera- ture approaches ambient temperature. When administrating clinical antiperspirant tests, one should avoid such high humidity conditions as condensation will likely occur. In our experience, we fi nd that high dewpoint temperatures make it extremely diffi cult for evap- orative cooling to take place. Much of the sweat remains on the skin surface, becomes hot, and does not allow new sweat to carry out cooling functions hence the body is unable to cool itself. A variety of other tests were also conducted and it was found that additional factors also infl uence the rate of sweating, such as water consumption, preconditioning climatic conditions, and exercise. Table II contains perspiration rates, again determined from the rate of perspiration between 25 and 45 min in the chamber, when other variables are introduced into the protocol. All of these clinical studies were conducted at a sauna Table II Perspiration Rates (g/min) at 45°C and 35% RH with the Infl uence of External Factors Subject 1 Subject 2 Left Right Left Right Control 0.0790 ± 0.001 0.0848 ± 0.005 0.0405 ± 0.002 0.0295 ± 0.002 Hot water 0.1020 ± 0.003 0.1019 ± 0.010 0.0639 ± 0.006 0.0562 ± 0.057 RT water 0.0829 ± 0.015 0.0799 ± 0.002 0.0464 ± 0.003 0.0321 ± 0.000 Bicycle for 15 min 0.1085 ± 0.002 0.1010 ± 0.000 Cold acclimatization 0.0238 0.0214 0.0170 0.0140