Heat exhaustion occurs when your body gets too hot. The hypothalamus, the part of the brain that controls thirst and hunger, also controls the body's core temperature. Normally, the body cools itself by sweating. When you are exposed to high temperatures for a long time (working outdoors in the summer, for example) and don't replace the fluids you lose, the body systems that regulate temperature become overwhelmed. As a result, your body produces more heat than it can release. Heat exhaustion requires immediate attention because it can progress to heat stroke, a life-threatening illness.
Signs and Symptoms
People with heat exhaustion may experience the following signs and symptoms:
- Pale, clammy skin
- Rapid heartbeat
- Dizziness, fainting
- Nausea, vomiting
- Muscle and abdominal cramps
- Mild temperature elevations
If body temperature goes above 104°F (40°C), or if coma or seizure occurs, the patient may have heat stroke. If left untreated, heat stroke can quickly lead to heart attack and death.
What Causes It?
Heat exhaustion occurs most often when you are exposed to high temperatures and become dehydrated, usually from not drinking enough fluids. It can also happen when you replace large volumes of sweat with fluids that do not contain enough salt.
Who's Most At Risk?
The following factors increase the risk of developing heat exhaustion:
- Being dehydrated
- Age (the elderly and children under 5 years of age)
- Illness or chronic disability
- Cardiovascular disease
- Respiratory disease
- Drinking alcohol
- Physical exertion in hot or humid environments (athletes, military personnel, and outdoor laborers are at high risk)
- Taking medications that interfere with the body's ability to cool itself, including antipsychotics, tranquilizers, antihistamines, tricyclic antidepressants, beta-blockers, and some over-the-counter sleeping pills
What to Expect at Your Provider's Office
If you have symptoms of heat exhaustion, you should see a doctor immediately. The doctor will perform a physical examination, check your blood pressure, pulse, and temperature, and assess how dehydrated you are. The doctor may also request lab tests of blood and urine samples.
If you are working or exercising in the heat, drink plenty of fluids before, during, and after the activity. Take the following precautions to prevent heat exhaustion:
- Try to stay in cool or air conditioned spaces on hot days.
- Drink more fluids than usual. Drinking fluids during exercise, for example, helps improve heart function, maintain kidney function, and lower the body's core temperature. Dehydration can stress the heart and reduce the kidneys' ability to maintain the correct balance of electrolytes (charged elements -- such as potassium, sodium, phosphorous, and chloride -- which are essential for the normal function of every cell in the body).
- Check in regularly with people who are vulnerable to heat exhaustion (the elderly, for example).
- Avoid alcohol.
- Drink water or sports drinks sweetened with natural juices.
- Exercise or work outdoors during cooler times of day.
- Drink 2 cups of water 30 minutes before exercising and drink 1 cup of water every 20 minutes during activity.
- Take cool baths.
- Wear loose, lightweight clothing.
- Long-term prevention of heat exhaustion includes regular, doctor-approved exercise. Those who exercise regularly over time, allowing their bodies to adjust to hot conditions, may better tolerate activity on warm days.
The primary treatment for heat exhaustion is to rest in a shady spot or, better, an air-conditioned room, and to drink cool (not icy) fluids. You can lower core body temperature by immersing yourself in cold water or spraying yourself with cold water and fanning. Water is usually enough to reverse dehydration, but you can also drink a sports drink that contains electrolytes.
Your health care provider may recommend an oral or intravenous saline electrolyte solution.
Complementary and Alternative TherapiesNutrition and Supplements
Health care providers may recommend drinking fluids that contain electrolytes (see Prevention section). Endurance athletes may want to take mineral supplements, including:
Foods high in these nutrients include dark leafy greens, nuts, seeds, whole grains, sea vegetables, blackstrap molasses, and bananas. Please note: Taking any of these minerals in large amounts may cause unwanted symptoms and/or mineral imbalances. Consult your doctor to determine the correct amount of mineral supplementation to meet your needs.Herbs
The most important treatment for heat exhaustion is replacing lost fluids by drinking water or a sports drink, and getting into a cooler environment. Some herbs may help, but if you have symptoms of heat exhaustion you should talk to your health care provider before taking anything. Although few studies have examined using herbs to treat heat exhaustion specifically, the following herbs may reduce fever or lower body temperature:
- Yarrow (Achillea millefolium ) -- used to treat fever. Do not take Yarrow if you are pregnant or nursing. Yarrow can have blood-thinning effects and should not be taken with other blood-thinning medications, such as warfarin (Coumadin), and should be discontinued at least 2 weeks before any surgery. Yarrow can interact with lithium and other sedative medications.
Although few studies have examined the effectiveness of specific homeopathic therapies, professional homeopaths may consider the following remedies for the treatment of fevers based on their knowledge and experience. Before prescribing a remedy, homeopaths take into account a person's constitutional type -- your physical, emotional, and psychological makeup. An experienced homeopath assesses all of these factors when determining the most appropriate treatment for each individual.
- Belladonna -- often used for fever, particularly if flushed with bright red skin and dulled mental activity. This treatment is appropriate for people who are not thirsty even though their mouths and skin are dry.
- Glonoinum -- used for fever if the person is flushed and sweaty. It's appropriate for people who complain of a hot face but cold extremities, as well as irritability, headache, and confusion. Homeopaths often recommend this treatment for ailments brought on by overexposure to the sun.
If you avoid heat stroke, recovering from heat exhaustion usually takes 24 to 48 hours. Depending on the severity of heat exhaustion, you may be hospitalized so doctors can monitor your fluid and electrolyte levels to avoid complications. Delayed access to cooling is the leading cause of complications among people with heat stroke. Heat exhaustion can exacerbate a wide range of medical conditions.
Your health care provider will check the fluid levels in your body to see if electrolyte replacement should be continued.
Aggarwal Y, Karan BM, Das BN, Aggarwal T, Sinha RK. Backpropagation ANN-based prediction of exertional heat illness. J Med Syst. 2007;31(6):547-550.
Becker J, Stewart L. Heat-related illness. Am Fam Physician. 2011:83(11):1325-1330.
Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs . Newton, Mass: Integrative Medicine Communications; 2000:103-105; 419-423.
Ferri FF. Heat exhaustion and heat stroke. Ferri's Clinical Advisor. Philadelphia, PA: Elsevier Mosby; 2015:532-533.e1.
Glazer JL. Management of heatstroke and heat exhaustion. Am Fam Physician . 2005 Jun 1;71(11):2133-2140.
Grove AJ, Gomez J. Environmental illness. In: Miller MD, Thompson SR, eds. DeLee and Drez's Orthopaedic Sports Medicine, 4th ed. Philadelphia, PA: Elsevier Saunders; 2014:272-284.e3.
Grubenhoff J, du Ford K, Roosevelt G. Heat-related illness. Clinical Pediatric Emergency Medicine. 2007;8(1):59-64.
Howe AS, Boden BP. Heat-related illness in athletes. Am J Sports Med. 2007;35(8):1384-1395.
Kim SH, Jo SN, Myung HN, Jang JY. The effect of pre-existing medical conditions on heat stroke during hot weather in South Korea. Environ Res. 2014;133:246-252.
Kravechenko J, Abernathy AP, Fawzy M, Lyerly HK. Minimization of heatwave morbidity and mortality. Am J Prev Med. 2013;44(3):274-282.
Tumilty L, Davison G, Beckmann M, Thatcher R. Oral tyrosine supplementation improves exercise capacity in the heat. Eur J Appl Pysiol. 2011;111(12):2941-2950.
Von Duvillard SP, Braun WA, Markofski M, Beneke R, Leithauser R. Fluids and hydration in prolonged endurance performance. Nutrition . 2004;20(7-8):651-656.
Yamazaki F. Effectiveness of exerciseheat acclimation for preventing heat illness in the workplace. J UOEH. 2013;35(3):183-192.
Review Date: 12/6/2014
Reviewed By: Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network. Also reviewed by the A.D.A.M. Editorial team.