Understanding Heat-Related Illness

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  • By Covenant Health
  • Medically Reviewed by Justin McGoldrick, MD
  • 8 minute read.

Identifying Heat Illnesses: Heat Rash, Heat Exhaustion, Heat Stroke and More

Sunny days can be inviting, but hot weather can also have consequences. The sun’s rays can cause sunburn and skin cancers and contribute to heat illnesses.

NASA has reported that summer 2023 was Earth’s hottest since global records began in 1880. According to the Centers for Disease Control and Prevention, heat-related emergency room visits totaled 119,605 in 2023 – a substantial increase compared to the previous five years.

Protect yourself, family and friends while enjoying the outdoors this summer – learn the various types of heat illnesses, their symptoms and treatments.

What Are Heat Illnesses?

High temperatures and humidity can cause heat-related illnesses such as heat cramps, heat rashes, heat exhaustion and heat stroke. The Department of Health and Human Services notes that about 700 heat-related deaths occur each year in the United States. Most heat illnesses in the U.S. occur between May and September when the sun’s UV rays are strongest. Extreme summer heat episodes are forecasted to be more frequent and intense, increasing the importance of knowing the signs and symptoms of heat-related illnesses.

There are several types of heat illnesses, including:

  • Heat cramps
  • Heat rash
  • Heat syncope
  • Heat exhaustion
  • Heat stroke
Matt Brannon, athletic trainer, Covenant Health Sports Medicine

“The most common types of heat illnesses are heat cramps and heat exhaustion,” says Matt Brannon, Covenant Health Sports Medicine athletic trainer. Brannon works with individuals at Morristown Landing in Morristown, Tennessee, where Covenant Health is the health partner of the community fitness and wellness center. He also works with student athletes participating in a variety of sports and competitions.

“Heat cramps typically occur during prolonged intense physical activity when a person either hasn’t adequately prepared for practice or competition through proper nutrition, hydration, rest or warm-up, or has a history of cramping,” Brannon says. “Heat exhaustion in young athletes typically occurs after prolonged exposure to the heat during conditioning [activities] and drills, after a period of little to no physical activity.”

What Are the Risk Factors for Heat Illnesses?

While anyone can suffer from a heat illness at any time, certain groups are at greater risk:

  • Children under 4 years old
  • Adults ages 65 and older
  • Pregnant women
  • People who are overweight
  • People with underlying health conditions such as diabetes and heart or kidney diseases
  • Those who are currently experiencing or recovering from illness
  • People who spend extended periods of time outdoors in physical work, exercise or athletics
  • Those who previously have experienced a heat illness
  • People without shelter

Using alcohol and taking medications that impair the body’s ability to regulate temperature or that affect hydration can also increase your risk of a heat-related illness. Environmental risk factors can play a role; people who are not accustomed to warmer temperatures can be more prone to heat illnesses. Heat waves and urban areas with more concrete and asphalt raise the outside temperature and can contribute to heat illnesses.

How Does Humidity Impact Heat Illnesses?

Humidity is the amount of water vapor in the air. While it doesn’t impact actual temperature, humidity can make the temperature feel hotter. Humidity prevents sweat from evaporating from the skin, causing heat to be retained and preventing the body from regulating its temperature.

When the body struggles to cool down, sweating can increase – which can lead to dehydration. Dehydration is a risk factor for heat-related illnesses and can impact other body functions and underlying conditions.

Heat Cramps Symptoms and Treatment

Heat cramps are often a result of exercising in the heat, leading to excessive sweating that causes a loss of the body’s electrolytes and fluids. The body’s temperature remains normal, but other symptoms include:

  • Cramps
  • Muscle pain or spasms in the legs, arms or abdomen
  • Cool, moist skin

To treat heat cramps, rest and drink water to replenish the loss of fluids. If cramps do not subside in one hour, contact a medical provider.

Heat Syncope Symptoms and Treatment

Heat syncope, or a sudden onset of dizziness, usually occurs after a period of heat exposure. It can be caused by dehydration, lack of acclimation to the heat, after standing for too long, or suddenly standing up after sitting or lying. Symptoms of heat syncope include:

  • Fainting
  • Dizziness and light-headedness

To treat heat syncope, sit or lie down in a cool place and slowly drink water, clear juice or a sports drink.

Heat Rash Symptoms and Treatment

Heat rashes occur when sweat gets trapped under the skin and blocks sweat glands. Symptoms of heat rash include:

  • Red or itchy skin
  • Pain that is tingly or prickly
  • Small bumps or blisters, particularly in the neck, groin, armpits, underneath breasts or in elbow creases

To treat a heat rash, go somewhere cool, dry your skin and use cold compresses. Avoid lotions or creams that can further block your pores.

Heat Rash vs. Sun Poisoning: What’s the Difference?

While heat rash occurs because the heat causes blocked sweat glands, sun poisoning is an extreme sunburn that can affect the body beyond the skin. Physical symptoms of sun poisoning include blistered skin, headache, nausea, dizziness and dehydration. Because sun poisoning is more extreme than a heat rash or sunburn, it can last for weeks and may require medical attention. Sun poisoning can be treated with cold compresses, steroids, lotions or topical antibiotics.

Heat Exhaustion Symptoms and Treatment

Extreme fatigue after prolonged activity in or exposure to heat can cause heat exhaustion. It is the body’s response to an excessive loss of water and salt from too much sweating. Symptoms of heat exhaustion include:

  • Excessive sweating and thirst
  • Reduced urine output
  • Headache and irritability
  • Muscle cramps
  • Weak, fast pulse
  • Nausea, vomiting or diarrhea
  • Dizziness or weakness
  • Cool, damp skin
  • Core temperature less than 105 degrees

To treat heat exhaustion, move to a shaded or cool area, remove unnecessary layers of clothing and lie down if you’re experiencing dizziness or weakness. Use cool showers or compresses to help decrease the body temperature and hydrate with water or sports drinks. If symptoms of heat exhaustion do not go away within half an hour, go to the nearest emergency room. If not treated in a timely manner, heat exhaustion can lead to heat stroke.

Heat Stroke Symptoms and Treatment

Most severe heat illnesses, including exertional heat stroke, occur when the body can no longer regulate its temperature. Heat stroke can be caused by overexertion and high temperatures.

Heat stroke is the most serious heat illness, Brannon says. “It is seen less frequently but leads to the most deaths in athletes, behind conditions and circumstances associated with sudden cardiac arrest.” Deaths from heat stroke “are largely preventable with proper planning, preparation, and the vigilance of medical and athletic staff.” Symptoms of heat stroke include:

  • Lack of sweating
  • Strong, fast pulse
  • Altered mental state
  • Slurred speech
  • Dry, hot skin
  • Hallucinations
  • Seizures
  • Hyperventilation
  • Loss of consciousness
  • Core temperature of 105 or greater, which can result in death if not treated quickly

If you believe you or someone else is experiencing a heat stroke, seek medical attention immediately. Until you can be seen by a medical professional, move to a shaded or cool area and remove unnecessary layers of clothing. Use a cold compress or a cold, wet cloth to lower body temperature.

Heat Exhaustion vs. Heat Stroke: What’s the Difference?

While heat exhaustion and heat stroke are both heat illnesses, heat stroke is much more serious, involves the central nervous system and requires immediate medical attention.

Extreme Heat Safety Tips

Brannon recommends these safety tips to help prevent heat illnesses:

  • Stay hydrated, eat enough and get enough sleep to help your body recover and prepare for activity.
  • Acclimate to heat by gradually increasing exposure and intensity of physical activities.
  • If possible, complete outdoor activities and exercises when the heat and humidity are at their lowest.
  • Take breaks in a cool, shaded place as needed and sip cool water or a sports drink during each break. Sports drinks with a lower sugar content are best when rehydrating to prevent increased nausea, vomiting or diarrhea.
  • Limit consumption of alcohol, caffeinated beverages and energy drinks before or after long periods in the heat.
  • Wear loose, lightweight, light-colored clothing with a wide-brimmed hat and sunglasses and apply sunscreen regularly. Sunburns lead to heat retention in the body and can contribute to heat illnesses.
  • Outdoor workers with limited shade should get into their vehicles with the air conditioning on if they experience symptoms of a heat illness.
  • Athletes playing outdoor sports should follow the guidance of certified athletic trainers and coaches regarding equipment worn during practices or any schedule changes related to the heat.

When to Contact a Health Provider

If you think you or someone else is experiencing a heat stroke, call 911 or go to the nearest emergency room immediately. If symptoms of heat exhaustion last more than 30 minutes, seek emergency care to make sure you’re not having a heat stroke. Covenant Health’s hospital emergency departments are open 24/7 throughout East Tennessee. Other heat illnesses like heat rash and heat cramps don’t usually require medical attention, but consult a provider if symptoms do not go away after home treatment.

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About the Author

Covenant Health

Headquartered in Knoxville, Tennessee, Covenant Health is a community-owned, healthcare enterprise committed to providing the right care at the right time and place. Covenant Health is the area’s largest employer and has more than 11,000 compassionate caregivers, expert clinicians, and dedicated employees and volunteers.

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