Ever notice how the droplets that appear on your forehead as you nervously await a big presentation smell worse than when you sweat through your shirt during a grueling workout? According to this video from Stuff Mom Never Told You, sweat is produced two ways, and one really reeks. Exercise sweat is mostly made up of water and, as a result, gives off very little odor. In contrast, anxiety sweat contains both water and proteins. These proteins react with bacteria on the skin to produce that BO smell we all love to hate.