Heat exhaustion is a severe form of heat illness. It is a medical emergency. Heat exhaustion is caused by the loss of water and sodium through sweating.
Symptoms of heat exhaustion include nausea, dizziness, irritability, headache, thirst, weakness, high body temperature, excessive sweating, and decreased urine output.[1]
First aid for heat exhaustion involves moving the affected person to a cool environment and administering cold liquids.[1]
If untreated, heat exhaustion may progress to heat stroke.[1]