Heat-Related Illnesses

Dr. Greene's Answer

Normal body cooling happens by sweating, but sometimes this natural process isn’t enough when temperatures are extreme (especially combined with exercise or improper clothing). Most heat-related illnesses occur in the summer. Groups who are most at risk for  heat injury include the young (0 to 4 years old) and elderly, outdoor workers, those with mental illness or chronic diseases, and even young healthy athletes if they are participating in strenuous physical activity in high outdoor temperatures. 

Children’s skin can be quite sensitive to heat. Nursing mom’s often discover this, especially in the summertime, when their baby’s face turns red where it is against the mother’s skin. This redness comes from blood vessels in the area dilating to cool the skin down. Cooling the skin usually makes the rash disappear within hours, or even sooner. Prickly heat (miliaria rubra) is a type of heat rash that lasts.

Heat-Related Illnesses

Heat cramps are the most common form of heat-related ailment. They most often occur when exercising in a warm environment, as sweating depletes the body of salt and water. This lowered salt level can lead to muscles cramping. The calf or hamstring muscles are most commonly affected and respond to gentle stretching and rehydration – especially with an electrolyte solution.

Heat syncope is fainting due to heat/dehydration. This is caused by dilation of the blood vessels to radiate heat. During heat syncope, the blood pressure is low and heart rate is elevated. This condition responds to cooling (like a sponge bath), lying down with feet up, and drinking fluids.  

Heat edema is swelling of the hands or feet from heat. People sometimes get this condition when initially exposed to hot weather, and it usually goes away as the person adjusts to the heat.

Heat tetany is tingling (especially of the wrists). Hyperventilation in hot weather can cause heat tetany.  The best way to treat this condition is to remove the person from the hot environment and work to slow their breathing. 

Heat exhaustion usually entails a temperature of 101 to 104, headache, nausea, vomiting, dizziness, and fainting. Heat exhaustion may occur gradually, over the course of several days of exposure to high temperatures. It is important to recognize and treat heat exhaustion immediately. Treatment includes cooling, fans, taking off extra layers of clothing, drinking liquids, and applying ice over the groin and armpits). People typically respond well, but prompt treatment is necessary in order to prevent the condition from progressing to heat stroke where treatment may no longer be effective.

Heat stroke is very serious. A person’s temperature rises over 104 degrees, and he or she has an altered mental status. There are two types of heat stroke — exertional, with profuse sweating, and classic, in which the skin is hot and dry. Classic heat stroke builds up over days, and is most common in infants and in the elderly. It is a true emergency. In the elderly population, up to 50% of those with heat stroke may die. Exertional heat stroke has a much better prognosis because it generally affects the young, healthy athlete and the diagnosis is often prompt, leading to a mortality of less than 5%. Both types of heat stroke are true medical emergencies and need to be recognized and treated immediately. . 

It is very important to take measures to protect yourself and others against these heat-related illnesses.  A few tips for prevention include staying out of direct sun during very hot days, avoiding strenuous physical activity during the hottest part of the day, wearing light colored clothing, wearing sunscreen and avoiding sunburns, staying hydrated (drink before you are thirsty!), and recognizing the first signs of any heat-related illness.  

Resources and References

CDC Extreme Heat Information. 

EpsteinY, et al. Heatstroke. The New England Journal of Medicine 2019; 380(25): 2449–2459.