Heat Exhaustion Symptoms You Should Never Ignore

Here's how to know when you need to cool off.

Heat-related deaths and illnesses are entirely preventable—and yet, extreme heat causes around 618 deaths in the United States each year, according to the Centers for Disease Control and Prevention (CDC).

Generally speaking, heat-related illnesses occur when the body isn't able to properly cool itself. Normally, the body cools itself automatically through sweating, but in cases of extreme heat, that's not always enough, the CDC says.

Heat exhaustion and heat stroke are the two main heat-related illnesses. Heat exhaustion is less severe than heat stroke and can develop after several days of exposure to hot temperatures and inadequate fluid intake. Heat stroke happens when the body's ability to cool off through sweating fails and you become unable to control your body temperature after it rises. During heat stroke, your body temperature can rise to as high as 106 degrees Fahrenheit in as little as 10 minutes, causing death or permanent disability if left untreated, according to the CDC.

While anyone can fall victim to heat exhaustion, it's most common in older adults and those with high blood pressure. People who regularly exercise outside in the heat are also prone to heat exhaustion, said Samantha Smith, MD, a Yale Medicine sports medicine doctor and assistant professor of clinical orthopedics and rehabilitation at Yale School of Medicine. "We increase our heat production up to 20-fold when we exercise."

Signs and Symptoms of Heat Exhaustion

Luckily, heat exhaustion has some key signs and symptoms that can make it easier to diagnose if you or someone you're with starts feeling unwell in the heat. According to the CDC, those symptoms include:

  • Heavy sweating
  • Paleness
  • Muscle cramps
  • Tiredness
  • Weakness
  • Dizziness
  • Headache
  • Nausea or vomiting
  • Fainting

How to Cool Down

Left untreated, heat exhaustion can progress into the more serious heat stroke. So, if you start to experience symptoms, there are measures you can take to nip the condition before it worsens. First, rest in a cool place, such as an air-conditioned room. If possible, take a cool shower, soak in a cool bath, or put towels soaked in cool water on your skin. Loosen clothing so air can circulate around your skin if a cool bath or shower isn't possible. "Lie on your back and raise up your legs so they are higher than the level of your heart," said Kirsten Bechtel, MD, a Yale Medicine emergency medicine doctor and associate professor at the Yale School of Medicine.

Hydration is also key. "Drink plenty of cool fluids," said Dr. Bechtel. "Stick to water or sports drinks. Avoid caffeinated or alcoholic beverages, as they can be dehydrating."

If taking these steps doesn't help you feel better, or your symptoms last longer than an hour or begin to worsen, it's important to seek medical care immediately.

Preventing Heat Exhaustion

If you know that you are going to be exposed to heat, wear lightweight clothing while you're outside. And if you're planning on exercising in a hot environment, give your body a chance to adapt to the temperature. "Healthy people can adapt to exercising and living in hot environments, but this takes some time, usually five days or more," said Dr. Smith.

It's also important to pay attention to the weather conditions, including the heat index. "Try to exercise in the cooler morning or evening hours," she said, stay hydrated before exercise, and replace what you sweat during and after your workout.

Overall, Dr. Smith advised to always "pay attention to your body—even more when conditions are very hot and humid" to prevent heat exhaustion and to stay safe in warm temperatures.

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