Heat Illness: Symptoms, Prevention, and Treatment

Nobody likes to be hot and sweaty on the trail. But when things turn from being uncomfortable to becoming downright dangerous, it’s time for quick, on-the-spot emergency action. 

Heat illness is a range of medical conditions that result from the body’s inability to cope with an elevated heat load. When that occurs, it is more commonly referred to as “heat strain.” And whether you’re inactive in a warm, humid environment or participating in strenuous physical activity in the fall or winter, you are at an increased risk of heat illness.

For people who engage in backcountry adventures, heat illness and heat strain are among the many potential health and safety risks. That’s why our instructors at The National Center for Outdoor Adventure Education (NCOAE) include it in our Wilderness Medicine courses. In this post, we bring you up to speed on the basics, including the symptoms to watch for, preventive measures, and treatments to cool an overheated body.

From Bad to Worse on the Heat Illness Spectrum

Heat illness, heat strain, and related injuries occur when the core body temperature becomes elevated, stressing or surpassing the body’s ability to cool itself. Like a nuclear power plant, the human body can suffer serious and potentially fatal damage when its core becomes overheated.

The severity of the condition is on a spectrum generally divided into the following three levels:

• Heat cramps
• Heat exhaustion
• Heat stroke

Heat cramps

Heat cramps are painful muscle spasms, often affecting the hands or legs, but also the back and abdomen. The exact cause is poorly understood but seems to be linked to dehydration — reduced levels of water and electrolytes.

The core body temperature remains normal, and at this level the condition is not life threatening, but it can be unpleasant. Consider it an early warning sign. By taking preventive measures when you first experience cramps, you can prevent the onset of more severe heat illness.

Heat exhaustion

At this point, body systems are starting to get overworked and are having trouble keeping body temperature regulated. The compensatory systems — like sweating — are still working, but this is your body telling you that you need to take a break and slow down before symptoms get worse.

Symptoms include headaches, body aches, muscle aches, nausea/vomiting, and lethargy. Core body temperature may be slightly elevated, but not severely.

Heat exhaustion is often associated with poor hydration (mild to moderate dehydration) and lack of adequate nutrition. Risk factors include physical exertion in hot and humid environments, lack of acclimatization, certain medications, and chronic health conditions or other illnesses.

Heat stroke

At this point, the body can no longer cool itself, and core temperature will rise to lethal levels if no action is taken. The core body temperature rises, typically reaching 104 degrees or higher. A core body temperature of 108 degrees can cause irreparable damage or death.

Symptoms include confusion or unresponsiveness, the body stops sweating, the skin becomes hot and dry, and breathing becomes shallow and rapid.

Heat stroke may or may not have anything to do with dehydration. Even with adequate fluid intake, if your core becomes too hot, you are at risk of developing this life-threatening condition.

Preventing Heat Illness

The best approach to heat illness is to prevent it, and while that may seem simple enough, there’s an art to accomplishing it in the backcountry. Whenever you are in a warm environment or are engaging in any strenuous physical activity, take the following precautions:

• Pay attention to the heat index, which is usually included in any weather forecasts for an area. The heat index reflects both temperature and humidity.
• Dress appropriately for the environment; for example, lightweight, nonrestrictive, light-colored clothing.
• If you aren’t accustomed to the heat and humidity of a new environment, acclimate yourself to it gradually.
• Rest during the hottest parts of the day.
• Hydrate properly with water and an electrolyte solution. Urine should generally be clear to light yellow in color. If you haven’t had to go in a while, or your urine is dark yellow or orange, drink more fluids. 
• Eat light meals and snacks consisting of easy-to-digest foods.
• Avoid alcohol, excessive caffeine, and supplements that stress on your body’s internal cooling system. (Workout and weight-loss supplements can be especially bad.)

Recognizing the Warning Signs of Heat Illness

The next best way to deal with heat illness (second only to prevention) is early intervention. Watch for the warning signs of heat illness. Listen to your body. If you start to feel tired or overheated, take a break. Sit in the shade, remove extra clothing, cool off with damp towels.

Watch out for your friends, too. If they start to drag or aren’t acting quite like themselves, get them out of the heat. Nausea, vomiting, and confusion are big red flags — warning you and others to ramp up your efforts to cool down your bodies.

Treating Heat Illness

Your approach to treating heat illness will vary according to its severity, as explained in the following sections:

Responding to heat cramps

Head for a shady location, hydrate with water and an electrolyte solution, eat a light meal (something that’s easy to digest), and rest. Then take it easy for a while.

Responding to heat exhaustion

Head for a shady location. Remove excess clothing, particularly hats, shoes, socks, and gloves — your head, hands, and feet are your body’s radiators. Drink cool fluids (water and an electrolyte solution) as tolerated — little sips to avoid nausea/vomiting. Wet your skin and fan it to promote evaporative cooling. 

If you have access to a cool body of water, use it to cool off. If you aren’t quite up to a swim, just immerse your hands and feet, splash water on your face, or sit in shallow area.

Once you feel better, rest and relax. Your body still has a lot of residual heat built up that will take time to dissipate. Don’t return to physical activity right away.

Treating heat stroke

Heat stroke is a life-threatening emergency. If the core body temperature is not reduced rapidly, death can result. Whenever symptoms of heat illness are severe, take immediate action:

• Rapid cooling is more important than transporting the victim. Early cooling decreases morbidity and mortality. Rule of thumb: You can’t cool someone off too fast when they are suffering heat stroke. 
• If possible, immerse in an ice water bath for 5 to10 minutes, agitating the water to speed the cooling process. Immersing in any cool body of water can help.
• Other methods include applying cold wet towels to the body, spraying cold water over the body continuously, or applying water to the body and fanning it to promote evaporative cooling. You can use a hose, shower, river, or lake and keep the water circulating around the body for 5 to10 minutes. If you are placing someone in a body of water to cool them, make sure you keep their head/face out of the water so they can breathe.
• If able, give oral rehydration — sugary electrolyte beverages, little sips at first — and pay attention to whether the person is urinating.
• If you are able, contact emergency services for help. Transportation to the hospital is recommended. But remember, cooling the body takes precedence over transport.
• If you are in a remote area, come up with an evacuation plan. Keep exertion to a minimum — only what is necessary for safety. Full recovery from heat stroke can take days to weeks. The person will be very sensitive to heat stress for a significant amount of time following a heat injury.

Remember, it takes a long time to get all that heat out of a person’s body, so just dumping a bottle of water on someone who’s overheated won’t cut it.

Regardless of the level of heat illness, it should never be ignored. As soon as you recognize the warning signs, take action. Get out of the heat, remove excess clothing, take steps to cool the body, rehydrate, and give your body enough time to recover.

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About the Author: Kate Javes is a North Carolina Level 1 Paramedic and EMT Instructor at The National Center for Outdoor & Adventure Education. A former two-sport NCAA Division I athlete at Rutgers University, Kate received her Bachelor of Science degree in math, and a second bachelor’s degree in history from the United States Naval Academy in Annapolis, Md.