Heat Stroke vs. Heat Exhaustion: What You Need to Know

July 17, 2019

If you’re out in the hot, humid weather of summer, be watchful for heat-related illness. Heat-related illnesses are brought on by heat, humidity and lack of hydration.

Heat-related illnesses include heat stroke and heat exhaustion, and it’s important to be able to spot them -- and take action, says Sean McNeeley, MD, Medical Director of UH Urgent Care.

Be especially aware with children, older adults and people with chronic illnesses, as they are much more vulnerable to the effects of heat, he says.

Signs of Heat Stroke

Heat stroke is a serious, life-threatening condition, but it is very different from a brain stroke.

Heat stroke happens when your body’s internal temperature rises to dangerous levels, and your body is unable to sweat enough to cool off. Heat stroke develops rapidly and needs immediate medical treatment. The effects of heat stroke can be serious – and often are fatal.

Warning signs of heat stroke can include:

Warm, dry skin
Rapid heart rate
Nausea, vomiting
Headache
Fatigue
Confusion, stupor

If you suspect someone has heat stroke, get the person out of the sun and heat and call emergency medical services right away. Until medical help arrives, you can apply ice packs to the groin or armpit and offer cool fluids if the person is alert and able to drink.

“If you suspect heat stroke, that’s a 9-1-1 call,” Dr. McNeeley says.

Heat Stroke Starts Out as Heat Exhaustion

Heat stroke is a severe form of heat-related illness called heat exhaustion, Dr. McNeeley says.

Warning signs of heat exhaustion can include:

Pale, clammy skin
Profuse sweating
Lightheadedness
Nausea, vomiting
Headache
Fatigue, weakness
Thirst
Dark urine

What to Do If You Suspect Heat Exhaustion

If you think you have heat exhaustion, Dr. McNeeley says it’s essential to immediately get out of the sun or heat and rest in air-conditioning or in front of a fan. Drink plenty of fluids, remove excess clothing and, if possible, take a cool shower, bath or sponge bath.

If you don’t feel better within about 15 minutes, it’s important to get medical attention at an urgent care, Dr. McNeeley says. Heat exhaustion can progress to heat stroke, which is life-threatening.

Heat exhaustion is not something you recover from right away, Dr. McNeeley says. It may take up to three or four days until your body is back to normal. During that time you’ll need to rest and stay out of the heat and humidity.

“You may need days to get better,” Dr. McNeeley says.

Tips to Avoid Heat-Related Illnesses

Dr. McNeeley offers these tips to avoid heat-related illnesses during a heat wave:

Keep drinking fluids. Your body needs time to absorb water, Dr. McNeeley says: “The hydration process doesn’t work minute to minute. Hydration has to get into your cells days ahead, and only some goes to your cells.” Keeping your system flush with fluids will help you avoid dehydration, the condition that sets you on the path toward heat exhaustion and stroke.

Schedule outdoor activities for the beginning or end of the day. Gardening or exercising outdoors is best done when temps are cooler. Stay inside with the air-conditioning or go to the mall or other air-conditioned place during the heat of the day.

Avoid caffeinated beverages and alcohol. Alcohol and caffeinated drinks such as coffee, tea or soda force your body to expel fluid and can set the stage for dehydration.

Watch the heat index. The heat index combines air temperature and relative humidity. When humidity is high, your sweat does not evaporate as quickly, reducing your body’s ability to cool itself. When the heat index is high, the potential for heat-related illness rises as well.

Stay out of direct sunlight. If you’re outside, stick to the shade as much as possible.

Wear white or light-colored clothing. Wearing black or dark-colored clothing will make you warmer in the sun because dark colors absorb light and convert it into heat. White or light-colored clothing reflects all light, so the light is not converted into heat.