A healthy body temperature is maintained by the nervous system. As the body temperature increases, the body tries to maintain its normal temperature by transferring heat. Sweating and blood flow to the skin (thermoregulation) help us keep our bodies cool. A heat-related illness occurs when our bodies can no longer transfer enough heat to keep us cool.
A high body temperature (hyperthermia) can develop rapidly in extremely hot environments, such as when a child is left in a car in the summer heat. Hot temperatures can also build up in small spaces where the ventilation is poor, such as attics or boiler rooms. People working in these environments may quickly develop hyperthermia.
High temperature caused by a fever is different from a high body temperature caused by a heat-related illness. A fever is the body's normal reaction to infection and other conditions, both minor and serious. Heat-related illnesses produce a high body temperature because the body cannot transfer heat effectively or because external heat gain is excessive.
Heat-related illnesses include:
Often, environmental and physical conditions can make it hard 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 or alcohol also increase your risk of dehydration.
Many medicines increase your risk of a heat-related illness. Some medicines 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 medicines can alter your sense of thirst or increase your body's production of heat. If you take medicines regularly, ask your doctor for advice about hot-weather activity and your risk of getting a heat-related illness.
Other things that may increase your risk of a heat-related illness include:
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 need immediate medical treatment.
Check your symptoms to decide if and when you should see a doctor.
When recognized in the early stages, most heat-related illnesses, such as mild heat exhaustion, can be treated at home.
Heat syncope (fainting) usually does not last long and improves when you lie down to a flat position. It is helpful to lie in a cooler environment.
Heat edema (swelling) is treated with rest and by elevating your legs. If you are standing for a long time in a hot environment, flex your leg muscles often so that blood does not pool in your lower legs, which can lead to heat edema and fainting.
Heat cramps are treated by getting out of the heat and replacing fluids and salt. If you are not on a salt- (sodium-) restricted diet, eat a little more salt, such as a few nuts or pretzels. Do not use salt tablets, because they are absorbed slowly and can cause irritation of the stomach. Try massaging and stretching your cramped muscles.
Heat rash (prickly heat) usually gets better and goes away without treatment. Antihistamines may help if you are having problems with itching. Keep areas clean and dry to help prevent a skin infection. Do not use baby powder while a rash is present. The powder can build up in the skin creases and hold moisture, allowing the growth of bacteria that may cause infection. Dress in as few clothes as possible during hot weather. Keep your home, especially sleeping areas, cool.
Call your doctor if any of the following occur during home treatment:
The following tips may help prevent a heat-related illness. Be aware of the symptoms of heat-related illnesses and the warning signs of dehydration.
Staying physically fit can help you acclimate a hot environment. Before you travel to or work in a hotter environment, use gradual physical conditioning. This takes about 8 to 14 days for adults. Children require 10 to 14 days for their bodies to acclimate to the heat. If you travel to a hot environment and are not accustomed to the heat, cut your usual outside physical activities in half for the first 4 to 5 days. Gradually increase your activities after your body adjusts to the heat and level of activity.
Be aware that when the outdoor humidity is greater than 75%, the body's ability to lose heat by sweating is decreased. Other ways of keeping cool need to be used. The National Weather Service lists a heat index each day in the newspaper to alert people of the risk for a heat-related illness in relation to the air temperature and humidity of that day. Direct exposure to the sun can increase the risk of a heat-related illness on days when the heat index is high.
People who have had heatstroke in the past may be more sensitive to the effects of heat in the first few months following the illness, but they do not have long-term problems.
To prepare for your appointment, see the topic Making the Most of Your Appointment.
You can help your doctor diagnose and treat your condition by being prepared to answer the following questions:
|Primary Medical Reviewer||William H. Blahd, Jr., MD, FACEP - Emergency Medicine|
|Specialist Medical Reviewer||H. Michael O'Connor, MD - Emergency Medicine|
|Last Revised||September 1, 2011|
Last Revised: September 1, 2011
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