Both conditions occur most often on hot days during physical activity. Anyone can have either condition, and either condition can happen to older people even during such mild activity as taking a walk. In heat stroke, the person's temperature control system that causes sweating stops working correctly. The body temperature rises so high that brain damage and death will result if the person is not cooled quickly. There may be dizziness, nausea, headache, rapid pulse, and unconsciousness.
Heat exhaustion is much less dangerous than heat stroke.
The major signs of heat exhaustion are pale, clammy skin, profuse perspiration, and extreme tiredness or weakness. The body temperature is approximately normal. The person may have a headache and may vomit. Here are the most important differences between the signs of heat stroke and heat exhaustion. Cool a person of heat stroke quickly.