Heat-Related Illnesses

Topic Overview 
By Healthwise 
A healthy body temperature is maintained by the nervous system) in the legs and hands, which can occur when you sit or stand for a long time in a hot environment. 
Heat tetany (hyperventilation and heat stress), which is usually caused by short periods of stress in a hot environment. 
Heat syncope (fainting), which occurs from low blood pressure when heat causes the blood vessels to expand (dilate) and body fluids move into the legs because of gravity. 
Heat exhaustion (heat prostration), which generally develops when a person is working or exercising in hot weather and does not drink enough liquids to replace those lost fluids. 
Heatstroke (sunstroke), which occurs when the body fails to regulate its own temperature and body temperature continues to rise, often to 105° (40.6°) or higher. Heatstroke is a medical emergency. Even with immediate treatment, it can be life-threatening or result in serious long-term complications.
Often, environmental and physical conditions can make it difficult to stay cool. Heat-related illness is often caused or made worse by dehydration and fatigue. Exercising during hot weather, working outdoors, and overdressing for the environment increase your risk. Caffeine and alcohol also increase your risk for dehydration.
Many medications increase your risk of a heat-related illness. Some medications decrease the amount of blood pumped by the heart (cardiac output) and limit blood flow to the skin, so your body is less able to cool itself by sweating. Other medications can alter your sense of thirst or increase your body's production of heat. If you take medications regularly, ask your health professional for advice about hot-weather activity and your risk of getting a heat-related illness.
Other factors that may increase your risk of a heat-related illness include:
•	Age. Babies lose heat quickly because they have a greater body surface area compared with their weight and do not sweat effectively. Older adults do not sweat easily and usually have other health conditions that affect their ability to lose heat. 
Obesity. People who are overweight have decreased blood flow to the skin, hold heat in because of their insulating layer of fat tissue, and have a greater body mass to cool. 
•	Summer heat waves. People who live in cities are especially vulnerable to illness during a summer heat wave because heat is trapped by tall buildings and air pollutants. 
•	Chronic diseases, such as diabetes, heart failure, and cancer. 
•	Travel to wilderness areas or foreign countries with high outdoor temperatures and humidity.
Most heat-related illnesses can be prevented by keeping the body cool and by avoiding dehydration in hot environments. Home treatment is usually all that is needed to treat mild heat-related illnesses. Heat exhaustion and heatstroke require prompt medical treatment. 
Review the Emergencies and Check Your Symptoms sections to determine if and when you need to see a health professional.