Heat exhaustion is the body's reaction to loss of body fluids through sweating when an inadequate amount of liquids have been consumed to compensate for the loss.
Heat exhaustion is characterized by fatigue, weakness, and even collapse.
The victim may be pale, tired, and have clammy skin with heavy sweating. Have the victim lie down. If vomiting occurs, do not give any more fluids. Usually the victim will recover with rest. Severe cases, though, may require a doctor's care.