Heat cramps are the mildest form of heat illness and consist of painful muscle cramps and spasms that occur during or after intense exercise and sweating in high heat. What is heat exhaustion? Heat exhaustion is more severe than heat cramps and results from a loss of water and salt in the body.

Syncope is also called fainting or "passing out." It most often occurs when blood pressure is too low (a condition called hypotension) and the heart doesn't pump enough oxygen to the brain. It can be harmless or a symptom of an underlying medical condition.