A shoe that fits well at the start may be too tight by the end of a run. Second, avoid cotton socks like the plaque. Cotton soaks up moisture and holds on to it. Socks made from synthetic fibers, such as Cool Max, will breathe better than cotton and keep feet dry. Socks that have seams can be worn inside-out to keep the seams from causing friction against the skin.
Friction causes blisters.
Third, products like Body Glide and Sport Slick applied to areas where blisters have been known to appear may reduce friction enough to ward them off. However, blisters sometimes happen, even if every precaution is taken to avoid them. Exercise caution when treating blisters and consult a medical professional if a blister appears to become infected. Infected blisters can lead to blood infections and other serious problems that can sideline a runner for an extended period of time. Hot and humid conditions are as much a part of a Chicago spring and summer as baseball and Lake Michigan.