Heat emergencies or illnesses are caused by exposure to extreme heat and sun. Heat illnesses can be prevented by being careful in hot, humid weather.
Heatstroke; Heat illness
Heat injuries can occur due to high temperatures and humidity. You are more likely to feel the effects of heat sooner if:
- You are not used to high temperatures or high humidity
- You are a child or an older adult
- You are already ill from another cause or have been injured.
- You are obese
- You are also exercising (even a person who is in good shape can suffer heat illness if warning signs are ignored)
The following make it harder for the body to regulate the temperature, and make a heat emergency more likely:
- Drinking alcohol before or during exposure to heat or high humidity
- Not drinking enough fluids when you’re active on warmer or hot days
- Heart disease
- Certain medicines: Examples are beta blockers, water pills or diuretics, some medicines used to treat depression, psychosis, or ADHD
- Sweat gland problems
- Wearing too much clothing
Heat cramps are the first stage of heat illness. If these symptoms are not treated, it can lead to heat exhaustion and then heatstroke.
Heat stroke occurs when the body is no longer able to regulate the temperature, and it keeps rising. Heatstroke can cause shock, brain damage, organ failure, and even death.
The early symptoms of heat cramps include:
Later symptoms of heat exhaustion include:
The symptoms of heatstroke include (call 911 or the local emergency number right away):
- Fever (temperature above 104 °F)
- Irrational behavior
- Extreme confusion
- Dry, hot, and red skin
- Rapid, shallow breathing
- Rapid, weak pulse
If you think a person may have heat illness or emergency:
- Have the person lie down in a cool place. Raise the person's feet about 12 inches.
- Apply cool, wet cloths (or cool water directly) to the person's skin and use a fan to lower body temperature. Place cold compresses on the person's neck, groin, and armpits.
- If alert, give the person a beverage to sip (such as a sports drink), or make a salted drink by adding a teaspoon of salt per quart of water. Give a half cup every 15 minutes. Cool water will do if salt beverages are not available.
- For muscle cramps, give beverages as noted above and massage affected muscles gently, but firmly, until they relax.
- If the person shows signs of shock (bluish lips and fingernails and decreased alertness), starts having seizures, or loses consciousness, call 911 and give first aid as needed.
- Do NOT give the person medications that are used to treat fever (such as aspirin or acetaminophen). They will not help, and they may be harmful.
- Do NOT give the person salt tablets without mixing the salt with water.
- Do NOT give the person liquids that contain alcohol or caffeine. They will make it harder for the body to control its internal temperature.
- Do NOT use alcohol rubs on the person's skin.
- Do NOT give the person anything by mouth (not even salted drinks) if the person is vomiting or unconscious.
When to Contact a Medical Professional
Call 911 if:
- The person loses consciousness at any time
- There is any other change in the person's alertness (for example, confusion or seizures)
- The person has a fever over 102 °F
- Other symptoms of heatstroke are present (like rapid pulse or rapid breathing)
- The person's condition does not improve, or worsens despite treatment
The first step in preventing heat illnesses is thinking ahead.
- Find out what the temperature will be for the whole day when you will be outdoors.
- Think about how you have dealt with heat in the past.
- Make sure you will have plenty of fluids to drink.
- Find out if there is shade available where you are going.
- Learn the early signs of heat illness.
To help prevent heat illnesses:
- Wear loose-fitting, lightweight and light-colored clothing in hot weather.
- Rest often and seek shade when possible.
- Avoid exercise or heavy physical activity outdoors during hot or humid weather.
- Drink plenty of fluids every day. Drink more fluids before, during, and after physical activity.
- Be very careful to avoid overheating if you are taking drugs that impair heat regulation, or if you are overweight or elderly.
- Be careful of hot cars in the summer. Allow the car to cool off before getting in.
- Never leave a child sitting in a car exposed to the hot sun, even after opening windows.
Winkenwerder W, Wawka MN. Disorders due to heat and cold. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 109.
Jardine DS. Heat illness and heat stroke. Pediatr Rev. 2007;28:249-258.
Platt M, Vicario S. Heat illness. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Mosby Elsevier; 2013:chap 141.
Jacob L. Heller, MD, MHA, Emergency Medicine, Virginia Mason Medical Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
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