The summer heat can be hard on your body. Extreme heat taxes the body’s cooling system. When humidity is high, sweat cannot evaporate efficiently, and core temperature climbs. Certain medications and an aging population magnify the danger.

Age makes it harder to stay cool

Older adults are more susceptible to heat-related illness for several reasons:

• Age can affect the body’s ability to regulate body temperature. For example, older adults produce less sweat, have reduced blood flow to the skin and experience decreased cardiac function, all of which limit their ability to regulate body temperature.
• Older adults may be taking multiple medications and have medical conditions that make it more challenging for their bodies to tolerate heat.
• Older people who have difficulty with mobility, live alone or lack access to air conditioning are at even greater risk.

Medications to watch out for

Certain medications can also interfere with the body’s thermostat, fluid balance or blood flow to the skin. These are some of the medicines that make heat more dangerous:

• Diuretics and laxatives may increase the risk of dehydration by removing fluid from the body. It is important to maintain hydration during heat waves.
• Antipsychotics used for mental health conditions can alter the body’s natural thermostat and reduce sweat production.
• Antihistamines used to treat allergies limit the body’s ability to dilate blood vessels, thereby reducing the skin’s ability to cool.
• Blood pressure medications decrease the amount of blood that the heart circulates. The blood doesn’t reach the skin as readily, and therefore, the heat is not dissipated from the body.
• Antidepressants may affect the brain’s ability to regulate temperature.
• Illicit drugs such as cocaine, heroin, methamphetamines and ecstasy can increase heat production in the body, which is very dangerous and can lead to death.
• Sedatives and alcohol can alter consciousness and make you less likely to recognize when the body is overheating.

People taking any of these classes of medications should talk to their doctor about appropriate precautions.

Weight can affect your body temperature

Overweight and obesity: People with obesity are at increased risk of heat-related illness. Body fat acts like insulation, making it more difficult for heat to be released through the skin. Additionally, those who are obese have altered sweat responses and higher body temperatures during physical activity, making them more susceptible to heat-related illnesses.

Underweight or malnourished: Underweight individuals have low muscle and fat mass, which diminishes their ability to store heat and respond to sweat, increasing the likelihood of heat exhaustion.⁹ Also, malnutrition increases the risk during heat waves.

The spectrum of heat-related illnesses

How dangerous is getting overheated? Heat-related illness can range from mild to life-threatening. These are the main categories:

• Heat rash is an inflammatory condition on the skin that arises from blocked sweat glands. It can sometimes lead to a skin infection.
• Heat cramps are painful muscle spasms caused by electrolyte imbalances resulting from prolonged exposure to high temperatures or intense physical activity.
• Heat edema is swelling of the feet or hands caused by heat-induced dilation of the blood vessels and resultant pooling of the blood.
• Heat syncope is a brief loss of consciousness or fainting that occurs due to heat exposure and subsequent dilation of the blood vessels. The blood is diverted away from the brain and towards the extremities, causing fainting.
• Heat exhaustion manifests with extreme fatigue, weakness, nausea, headache and an elevated body temperature (less than 104 F). It is caused by loss of fluid and electrolytes during exposure to heat. A person with heat exhaustion appears ill but is not losing consciousness or confused.
• Heat stroke is the most severe form of heat illness, occurring when a person’s body temperature exceeds 104°F, as the body loses its ability to regulate its temperature. It can cause seizures, confusion, loss of consciousness or coma. This is very dangerous because it can cause organ failure and death if not treated urgently.

Heat rash, heat cramps, heat edema and heat syncope are considered milder forms of illness; however, they can be particularly dangerous in individuals with underlying health conditions. Heat exhaustion is more serious and often requires treatment in the emergency room. Heat stroke is the most dangerous form and can be deadly.

How to tell if someone has heat illness

Individuals who have been exposed to high temperatures, lack access to air conditioning, and engage in physical activity are at a higher risk of developing heat-related illnesses. Here are some of the signs:

Early heat-related illness

People with early heat-related illness may show the following signs:

• Muscle cramps
• Fatigue
• Headache
• Dizziness or lightheadedness
• Cool, moist skin
• Increased thirst
• Increased sweating

Heat exhaustion and syncope

Heat exhaustion and syncope are more serious. Here are some of the signs:

• Profuse sweating
• Pale, clammy skin
• Increased heart rate
• Nausea and vomiting
• Dizziness or fainting
• Headache
• Elevated body temperature (but less than 104 F)
• Weakness and extreme fatigue

Heat exhaustion requires prompt attention and treatment.

Heat stroke

Heat stroke is life-threatening and a medical emergency. Here are some signs:

• Body temperature 104 F or higher
• Confusion or slurred speech
• Seizures
• Losing consciousness
• Nausea and vomiting
• Elevated heart rate and breathing
• Hot, red and dry skin because they have stopped sweating

While early-stage heat-related illnesses can usually be managed at home, heat exhaustion and heat stroke require immediate medical attention. Call your doctor to get the help you need.

Recognizing the signs of heat-related illness can help you intervene early and save a life.

Prevention: heatwave safety tips

There are several ways that you can prevent heat-related illness, and know your limitations:

• Limit strenuous activity outside to the morning and evening, and avoid the hottest part of the day. It is important to stay active, but protect yourself.
• Drink fluids according to your level of thirst with water or an electrolyte drink. This is especially important for older adults.
• Use cooling strategies such as shaded rest breaks, fans, cool showers, air conditioning or public cooling centers.
• Check on vulnerable neighbors, particularly older adults and those without air conditioning, to ensure their well-being.
• Acclimatize gradually by increasing exposure slowly over 10 to 14 days at the beginning of the hot season.

Certain groups should be particularly cautious about preventing heat-related illnesses, including older individuals, those who work outdoors and athletes.

Staying safe in the heat of summer

As temperatures rise and the extreme heat of summer is the daily norm, understanding the signs of heat-related illness is more important. Timely recognition and response can save lives. While older adults, individuals with chronic health conditions, and those taking certain medications are particularly vulnerable, everyone should take precautions during heat waves. Plan outdoor activity wisely, stay hydrated, and check on those at risk to stay safe. Heat-related illness is preventable and treatable with awareness and fast action.

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This information is for educational purposes and is not a substitute for professional medical advice. If you suspect heat stroke, call emergency services immediately.