## 4 Discussion
Past publications have shown that a humid climate increases skin moisturization (coroneometric measurements) and friction behavior with more sticky sensations; stronger effects were observed on the forearm compared to the cheek [38; 39]. More recent investigations demonstrated a clear influence of seasonal climate variation on skin biophysical parameters of volunteers living in the same country and city [40; 41]. Impacts of air temperature, relative humidity, amount of precipitation, air pressure and duration of sunshine were found on skin scaliness (Visioscan(r) analysis, Courage & Khazaka, Koln, Germany) and moisturization (coronemeter) in a cohort of 89 Korean women, 20 minutes' acclimatization at 22 \(\pm\) 2 \({}^{\circ}\)C and 50 \(\pm\) 5% relative humidity [40]. A second analysis, carried out in China on 178 women with phototypes II to IV, resulted in a positive correlation between skin hydration (coronemeter) and temperature and to a lesser extent with humidity [41]. In the same work, TEWL was negatively correlated with average temperature and, to a lesser extent, with humidity and ultraviolet radiation levels. The current studies were conducted between April and September which represented very different climatic conditions depending on the location, as featured in Table 3. The Brazilian volunteers lived in a polluted megacity with large temperature fluctuations (amplitude of 24 \({}^{\circ}\)C) and a high amount of sunshine. The French volunteers lived in a medium-sized city near the ocean and were subjected to the lowest temperatures (average of 13 \({}^{\circ}\)C; amplitude of 25.5 \({}^{\circ}\)C), associated with the lowest relative humidity and the highest amount of sunshine. The Indian volunteers lived in a polluted megacity and were exposed to the most humid conditions with very high precipitation levels and the most stable temperature (amplitude of 11 \({}^{\circ}\)C; low amount of sunshine). The Mauritian volunteers lived in the lowest polluted environment with the most temperate weather (dry winter season, low amount of sunshine). Only volunteers from Mauritius were exposed to constant windy conditions at an average speed of 42.5 km/h, because of their location in the Indian Ocean (wind speed \(\leq\) 25 km/h in other locations). The common point between these different natural surroundings was a high relative humidity. Given the diversity of volunteers to which cultural and individual variability must be added, consistent effects were observed. Experiments were conducted on two body sites: leg and forearm. Both areas are likely to be exposed to the sun which could affect skin hydration [8]. In the literature, volunteers who were located in diverse geographical areas consistently showed no variation in TEWL \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Country** & **Brazil** & **France** & **India** & **Mauritius** \\ \hline
**City** & **Sao Paulo** & **Bordeaux** & **Mumbai** & **Curepipe** \\ \hline Lowest temperature (\({}^{\circ}\)C) & 9 i & 2.5 i & 24 i & 15 i \\ Highest temperature (\({}^{\circ}\)C) & 33 i & 28 i & 35 i & 25 i \\ Mean temperature (\({}^{\circ}\)C) & 19 i & 13 i & 29.7 i & 20 i \\ Air pressure at sea level (hPa) & 1017 i & 1015 i & 1004 i & 1018 i \\ Relative humidity (\%) & 81 j & 71 j & 83 j & 79 n \\ Cumulative precipitations (mm) & 143 i & 40 i & 487 m & 73 i \\ Cumulative sunshine (h) & 102 i & 197 i & 55 k & 43 k,m \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Average climatic conditions in the month before each test (year of the study). between the two body sites, even across different age groups and gender [42; 43]. Conversely, a tendency of higher skin conductivity was reported [42], while in the second publication significantly higher skin conductivity was reported in two groups of volunteers from 25 to 50 years old [43]. Thus, the site of the body could affect the result. Previous studies on glucolipid emulsifiers were conducted on forearms [16; 17; 18; 19; 21].