Sweat can be detrimental to an athlete, especially in tennis, in which having dry or sweaty hands can be the difference between hitting a winner and sending the ball flying to no-man’s land. Sweat is a normal function of the human body that helps regulate body temperature. The sympathetic nervous system, responsible for the fight-or-flight response, controls your sweat; when your body is on heightened alert, like in a competitive tennis match, you sweat. Of course, playing in hot weather conditions can also make you sweat excessively.
Consume foods that contain sodium. This may help you to retain more water and control your sweaty hands. It is better to eat healthy foods that contain sodium than junk foods; opt for chicken broth or vegetable juice rather than French fries or potato chips.
Wear wristbands and change them frequently throughout your match. Wristbands can soak up the sweat on your face and hands during a match without having to go to the sidelines, which is not always possible between points. However, the more you sweat, the less absorbent the wrist bands will become, so change them often during changeovers.
Change your racquet overgrip before your match. Overgrips can help to keep the racquet from sliding around in your hand. This becomes even more important during excessively hot days. Depending on the particular grip, it may lose its friction after several matches. Put a new grip on your racquet before each match to ensure that it is at its most abrasive.
Bring plenty of towels to the match. Towels are one of the most effective ways, and at times the only way, to control and mop up the sweat on your hands, arms and face during a match. Use the towels during changeovers, and place a towel behind or to the side of the baseline for easy access between points.
Visit a doctor and make sure that you do not have any medical conditions -- such as palmar hyperhidrosis -- that are contributing to sweating excessively. In some cases, palmar hyperhidrosis can be alleviated through minor surgery or topical treatments.
Experiment with the use of wristbands during practice. As they provide a new sensation, get accustomed to them before wearing them for competition to avoid distraction.