Heat exhaustion is also caused by loss of salt and water contained in sweat. Elderly people, people with high blood pressure, and people who are working out in a hot environment are most prone to this condition. Loosen or remove clothing. Drink lots of cool, non-alcoholic beverages. Be evaluated by a doctor.
Heat stroke is the most serious heat-related illness.
The person with heat stroke suffers rapid rise in body temperature and loss of the sweating mechanism. This is a true emergency - body temperature can rise to 106 degrees rapidly. Call 911 immediately. Get the victim out of the heat. Cool him or her rapidly using whatever method you can, such as spraying with a garden hose or wrapping in wet sheets.