Also, understand that the rate of fluid loss through sweating usually exceeds the rate of absorption of ingested fluids. Thus, hyperhydrating before a competition by drinking 13 - 20 ounces of cold water or an electrolyte solution can help delay the process of dehydration. Loose, lightweight material allows for better air circulation and facilitates evaporation of sweat. Dry clothing slows down evaporation of sweat, but once wet, cooling continues. Thus changing into dry clothing is not a good idea.
Sweat becomes more dilute.
The threshold at which sweating begins is lowered and the sweat rate is increased. Antihistamines and some blood pressure medications decrease sweating. Caffeine and alcohol are diuretics and cause your body to lose water. You should avoid their use. Follow this simple procedure to determine how much more fluid you may need in the hot conditions.