How Are Heatstroke and Heat Exhaustion Different?

Despite their similarities, heatstroke and heat exhaustion have different effects on the body. Heat exhaustion relates to dehydration and subsequent struggle of the heart to pump blood throughout the body. Heatstroke occurs when a person’s body temperature gets so dangerously high that it begins overheating the tissues and organs, says William Roberts, MD, a professor of family medicine and community health at the University of Minnesota in Minneapolis.

People can usually treat heat exhaustion with cold water, cool air, and rest. Heatstroke is an emergency medical condition that requires immediate care.

Although heatstroke might appear to progress from heat exhaustion, Dr. Roberts says that a person may not show signs of heat exhaustion before experiencing heatstroke. “You can go right there without the intervening step,” he says. In any instance, swift attention is key to avoiding complications of both heatstroke and heat exhaustion.

Recognize the Warning Signs

Heat exhaustion and heatstroke share many of the same warning signs, with a few key differences. “To the naked eye, it’s difficult to distinguish between heat exhaustion and heatstroke. To differentiate between the two, you need to know if the person’s brain is working well and what their body temperature is,” says Roberts.

Symptoms of Heatstroke

• Hot, red, dry, or damp skin, if the person has been exercising
• Fast, strong pulse, becoming weak as heatstroke progresses
• Headache
• Dizziness
• Nausea
• Passing out
• Movement and balance issues
• Lung crackles or abnormal breathing
• Making very small amounts of urine
• Weakness

Symptoms of Heat Exhaustion

• Heavy sweating
• Fast, weak pulse
• Nausea or vomiting
• Muscle cramps
• Tiredness or weakness
• Dizziness
• Headache
• Passing out
• Cool, pale, clammy skin
• Elevated body temperature, but typically less than 103 degrees F

How to Treat Heat Exhaustion or Heatstroke

Since heat exhaustion and heatstroke are separate medical conditions, the treatments differ. If you suspect that you or someone you know is suffering from heat exhaustion, a few steps can help that person to start cooling off and rehydrating while waiting for medical help.

Heat Exhaustion Treatment

• Drink cold beverages that don’t contain any alcohol or caffeine
• Cool off in the shade
• Stay indoors with air-conditioning or a fan
• Take a cool bath or shower
• Remove excess clothing

Rest is also key because it reduces strain on the cardiovascular system and helps stabilize body temperature.

Heatstroke Treatment

Heatstroke, on the other hand, is a life-threatening condition that requires emergency treatment. Without medical intervention, the condition can quickly cause brain, heart, kidney, and muscle damage or failure, and it can be fatal.

When caring for someone you suspect has heatstroke, the first thing you should do is call an ambulance. While you wait for medical professionals to arrive, try to lower the person’s body temperature in the following ways:

• Move the person to a shaded or air-conditioned area to cool down.
• If possible, place them in a cool bath or shower or cool them with water from a garden hose. According to a meta-analysis of 63 studies on heatstroke treatment methods, submerging a person in cold water — about 34 to 63 degrees F — is the most effective method to lower core body temperature.

• Importantly, Mayo Clinic advises against giving a person with heatstroke anything to drink.
   Many people with heatstroke have an altered mental state, which could make it unsafe for them to drink fluids.

Preventing Heat-Related Illness

According to Barrak Alahmad, MBBS, a physician and mission scholar in the faculty of public health at Kuwait University and a PhD student at Harvard University's T.H. Chan School of Public Health in Boston, heatstroke and heat exhaustion are completely preventable.

“High temperature, high humidity, and extensive physical activity trigger both,” he says, noting that as a first step, early warning systems can help alert the public of extreme-heat days so they can prepare to stay out of potentially dangerous heat.

• Gradually build up to heavy exertion
• Take breaks as often as possible in a shaded or cool area
• Be aware that protective equipment required by the job can sometimes increase the risk of overheating

If you need to be outside on a hot day, be sure to wear:

• Light clothing (both in color and fabric)
• A hat
• Sunscreen

“Getting into air-conditioning for as little as 30 minutes a day can make the difference between fatal heatstroke and not,” says Roberts, who recommends exercising with a buddy so you can look out for each other.

Since alcohol dehydrates the body, it’s best not to drink it in extreme heat. “It’s important to maintain good hydration, and don’t let yourself get thirsty,” says Roberts, who says that no one-size-fits-all daily water intake is safe or helpful, as everyone needs different amounts. “Recommending a certain amount is a recipe for overhydration, which can also be dangerous. Just drink when you are thirsty, and don’t let your urine get dark yellow,” he says.

The Takeaway

Heatstroke is more dangerous than heat exhaustion, as it can lead to organ failure and even death. But heat exhaustion can lead to heatstroke, and people need to take caution to prevent both in extreme heat, especially if they’re very active or work outdoors. Because it can be difficult to differentiate between the two, do not hesitate to call 911 if someone is showing symptoms.

Additional reporting by Lisa Rapaport.