Gradual exposure to the sun and heat for about a week results in some degree of heat tolerance, but even people acclimated to hot weather are subject to heat stress. The first sign is often mental confusion or a decrease in the ability to think and reason clearly. Unfortunately, these symptoms are very subtle and the affected person usually doesn't notice the change. This makes heat stress a serious condition because the person doesn't rest or allow for a recovery period. Other signs include cramps involving the extremities and abdominal muscles.
Cramps occur when the body loses water faster than it can replace it.
This is a more serious illness and is caused by excessive sweating and severe loss of water and salt. Excessive sweating causes dehydration, which strains the circulatory system. Without proper treatment, it can result in physical collapse. Symptoms of heat exhaustion include moist, clammy skin which appears ashen and gray, enlarged pupils, confusion, vomiting and weakness. Treat people by placing them in a cool environment, give them water or other cool fluids and sponge them down with water.