This setting powder is straightforward.  It's used after foundation and blush/bronzer to keep the makeup last long and to keep urban pollutants/smog and dirt/dust from getting absorbed. I've been using it in the winter and expect that it'd work even better during the hot and humid months.  As it is, it's kept my foundation looking good and meant less need for touchups throughout the day.  So far, it hasn't caused any reactions or skin irritation.