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Heat Stroke: Causes, Symptoms, Prevention, and Treatment

Heat stroke is a life-threatening medical condition that occurs when the body’s core temperature rises to dangerous levels, typically above 40°c (104°C). Heat strokes typically occur due to prolonged exposure to high temperatures or intense physical activity in hot environments. It is critical to understand that heat stroke is a severe life-threatening condition requiring immediate medical attention.

Heat Stroke
Heat stroke is a life-threatening condition caused by exposure to extremely hot temperatures

Heatstroke manifests as a number of symptoms, including (but not limited to) fatigue, dizziness, muscle cramps, nausea, and loss of consciousness. These symptoms emerge as overheating disrupts the body’s neurological, cardiovascular, and gastrointestinal systems.

Heat strokes are most prevalent in urban areas, particularly among the residents of upper-floor flats and overcrowded living quarters. However, heat stroke may affect anyone exposed to extreme heat, and is especially risky for older people and those with chronic illnesses.

It’s possible to prevent heat stroke by staying hydrated, avoiding physical activity in hot environments, wearing loose, breathable clothing, and seeking shade during the hottest parts of the day. However, heat stroke prevention strategies may differ depending on whether a person is at home, outdoors, in transit, or at work. Children, the elderly, and pets have unique vulnerabilities during periods of intense heat and require tailored heat stroke prevention strategies.

Heat stroke is a potentially fatal condition, so getting emergency medical assistance is vital if you or someone you know is showing symptoms of the condition. Read more below to get a comprehensive overview of heat stroke, including its definition, symptoms, complications, as well as heat stroke prevention and treatment.

What is heat stroke?

Heat stroke (also known as sunstroke, thermic fever, and siriasis) is a life-threatening condition in which the body temperature rises to above 40°c (104°f) and loses its thermoregulatory functions. Heat stroke occurs as a result of prolonged exposure to extreme heat or overexertion in hot weather.

There are two main types of heat stroke: non-exertional heat stroke and exertional heat stroke. Non-exertional heat stroke (NEHS) (also known as “classic heatstroke”), is caused by prolonged exposure to high temperatures. NEHS occurs without physical exertion and takes several hours to a few days to develop. Conversely, exertional heat stroke (EHS) is the result of intense physical activity in hot environments. EHS can develop within hours, or even minutes, due to the combination of physical activity and high temperatures. Both types of heat stroke share common symptoms, complications, and risk factors, although healthy and physically active people are more likely to experience exertional heatstroke. Meanwhile, non-exertional heat stroke affects many types of individuals, including vulnerable adults and children, and those exposed to hot environments without adequate hydration and protection from the sun.

Heat stroke is not the only condition that develops in response to overheating, dehydration, or overexertion in hot environments. Below are eight illnesses that develop in extremely hot environments and often display similar symptoms to heat stroke.

  • Heat syncope: Heat syncope (also known as orthostatic dizziness) is an episode of dizziness or fainting due to a drop in blood pressure.  The blood pressure drop that triggers heat syncope occurs because of prolonged standing or sudden changes in body position (such as standing up too quickly) in high temperatures. Heat-related dehydration is a common contributing factor to heat syncope. Seek emergency medical help if someone you know faints or becomes dizzy due to heat.
  • Heat oedema: Heat oedema refers to the swelling of the hands, feet, or ankles due to prolonged exposure to high temperatures. Heat oedema occurs when the blood vessels in these areas expand (dilate), causing fluid to accumulate in the joints. You’re able to reduce heat oedema symptoms by getting out of the hot environment and elevating your feet. However, it’s important to get professional medical advice if you experience this condition, as oedema often points to an underlying medical condition. Seek emergency medical assistance if other symptoms of heat stroke accompany heat oedema.
  • Heat tetany: Heat tetany refers to heat stress and hyperventilation. Heat tetany is characterised by involuntary muscle contractions, numbness or tingling in the extremities, and a feeling of tightness in the chest. Prolonged exposure to heat and humidity is the typical trigger for heat stress and hyperventilation, and the condition may progress to muscle cramps and spasms if the individual does not cool off as symptoms develop. Cooling off and rehydrating are the first two steps in treating heat tetany, but emergency medical help may be necessary if other symptoms of heat stroke are present.
  • Heat urticaria: Heat urticaria is a skin condition that results in the development of itchy hives, or welts, on the skin due to exposure to heat. Heat urticaria typically causes hives to appear within minutes of exposure to intense heat and may be accompanied by other symptoms, such as swelling and redness. Treat heat urticaria by getting out of the hot environment, rehydrating, and seeking professional medical assistance. A medical professional should be able to recommend a suitable topical or oral treatment for the condition.
  • Heat exhaustion: Heat exhaustion symptoms are comparable to those caused by heatstroke, including weakness, dizziness, headache, nausea, increased heart rate, sweating, and exhaustion. Untreated heat exhaustion can progress to a heat stroke, which can be life-threatening. It is important to treat heat exhaustion as soon as possible to prevent it from developing into heat stroke. Heat exhaustion and heat stroke symptoms may be difficult to tell apart, so it’s always best to seek professional medical assistance if you’re not sure whether you, or someone you know is experiencing this condition.
  • Dehydration: Dehydration is a state in which the body’s supply of fluids becomes depleted when the body loses more water than it takes in. Excessive sweating coupled with insufficient fluid intake is a common cause of dehydration. Symptoms of heat-related dehydration include extreme thirst, dry mouth, dizziness, headaches, tiredness, dark urine, and muscle cramps. Severe dehydration can lead to organ failure or death if left untreated, especially when it’s a symptom of heat stroke. Treat dehydration by drinking fluids with electrolytes (such as a sports drink), cooling off, and getting rest. Get emergency medical assistance if dehydration is accompanied by other symptoms of heat stroke.
  • Heat cramps: Heat cramps are painful muscle spasms that occur during or after vigorous physical activity and profuse sweating in hot environments. Symptoms of heat cramps include intense pain and spasms in the muscles that have seen repeated use during exercise or labour. Heat cramps are the mildest form of heat-related injury, for which rest, cooling down, and intake of electrolyte-containing fluids are the most effective treatments.
  • Heat rash: Heat rash (referred to as “prickly heat”) is a skin irritation caused by the obstruction of sweat glands during periods of excessive perspiration in hot weather. Symptoms of heat rash include red bumps on the skin, itching or stinging sensations, and occasionally a fever. Treat a heat rash by getting to a cool place, rehydrating, then cooling your skin with a damp cloth or cool shower, and letting it air-dry. Avoid using pore-blocking products like oily moisturisers, cosmetics, and sunscreens. Use a lanolin-based moisturiser to prevent clogged sweat ducts.

Why does heat stroke occur?

Heat stroke occurs because prolonged exposure to heat or strenuous activity impairs the body’s ability to self-cool, and the increasing body temperature disrupts vital bodily functions.  

The body’s ability to control its temperature is known as “thermoregulation”. Heat stroke triggers such as extreme heat, physical exertion, and dehydration disrupt thermoregulation, and the function begins to shut down once the body reaches temperatures above 40°C (104°F). The body loses its ability to cool itself down through the production and evaporation of sweat, and the ensuing hyperthermia (severe overheating) begins to dilate blood vessels and temper with the electrolyte balance. Dilated blood vessels lead to low blood pressure and thus a decreased supply of oxygen to the body’s vital organs. The heat-induced electrolyte depletion impairs neurological, digestive, and cardiovascular functions.

Where do most heat strokes occur?

Most heat strokes occur in urban settings during times of extreme heat. The two groups of people who are particularly vulnerable to heat stroke in cities are as follows.

  • People living in upper-floor flats: Statistics show that the most severe cases of heat stroke happen to people who live in top-floor flats. Top-floor dwellers are at a higher risk of heat stroke for two reasons. Firstly, heat accumulates on a building’s top floors because hot air rises and cool air sinks. This heat accumulation leads to elevated indoor temperatures that may be a few degrees higher than those in low-floor flats. Secondly, top-floor flats are more exposed to sunlight, and may often have limited shade or ventilation compared to lower floors. This prolonged exposure to solar radiation raises the room temperatures and thus heightens the risk of heat-related illnesses, such as heat stroke or heat exhaustion. Residents of highrise buildings without air conditioning are particularly susceptible to heat stroke during severe heat waves.
  • People living in overcrowded conditions: People who live in overcrowded housing (such as homeless shelters) are notably vulnerable to heat-related illnesses for two reasons. Firstly, overcrowded living quarters accumulate and retain heat during heat waves due to poor ventilation and lack of air conditioning. Secondly, vulnerable people who generally reside in overcrowded conditions are often unhealthy, and their poor health further exacerbates the effects of extreme heat and increases the risk of severe heat stroke.

However, heat stroke can occur anywhere where temperatures are hot enough to trigger the condition in a person. Heat strokes may occur at home, during travel and outdoor activities, at events, and at the workplace. Inadequate ventilation, lack of air conditioning, physical exertion, limited shade, and dehydration are factors that increase the risk of heat stroke during periods of hot weather.

When do heat strokes mostly occur?

Heat strokes mostly occur during the hottest part of the day, especially in hot climates or during a heatwave. In the UK, heat stroke is most likely to occur during summertime, especially between July and August, when excess mortality rates during heat periods are at their highest. The UK Health Security Agency (UKHSA) recommends staying out of the sun and avoiding strenuous physical activity between 11am and 3pm during high temperatures, as heat stroke most commonly occurs between these hours.

Research indicates that heat stroke is much more likely to occur during periods of both high temperature and high humidity. The combination of heat and humidity hinders the body’s ability to cool itself through sweat evaporation, leading to a greater likelihood of heat-related illnesses, including heat stroke. The heat index measures how hot the air actually feels to the human body, by combining the actual air temperature with the relative humidity. A heat index of 40°C (104°F) or higher suggests high relative humidity and an increased risk of heat stroke, especially during prolonged exposure or extensive physical labour in a hot environment.

Is a heat stroke dangerous?

Yes, heat stroke is dangerous. Heat stroke is a serious medical condition that requires rapid diagnosis and prompt intervention. The worst-case scenarios for heat stroke victims include multiple organ failure, brain trauma, and death.

The long-term health implications of heat stroke vary between individuals and are affected by medical response time. Heat stroke is more likely to have fatal or long-lasting consequences in vulnerable populations, such as the elderly or those with preexisting health conditions. Some statistics suggest that non-exertional heat stroke can prove fatal in up to 65% of cases.

Heatstroke-related deaths in the UK fluctuate annually, depending on various factors like weather conditions and individual vulnerability. Recent data from the Office of National Statistics (ONS) shows that an average of 1,272 fatalities occur annually due to extreme weather conditions, and there are an additional 12,086 hospitalisations associated with hot days. It is important to understand that while high temperatures may contribute to higher mortality rates, they do not necessarily indicate heat stroke as the cause of death. However, certain consequences linked to severe heat damage, such as vital organ failure, may have hastened some deaths in the more vulnerable populations.

It’s worth noting that heat stroke fatalities in milder countries like the UK are fairly infrequent compared to regions that regularly experience extreme heat. However, fatalities caused by heat stroke become more common during intense heat waves or unusually high temperatures.

When to go to the hospital with a heat stroke?

Go to the hospital (ideally via ambulance run) any time you or someone you know experience symptoms of heat stroke or have not responded to heat exhaustion treatment within 30 minutes. You should perform the following six steps whilst waiting for the paramedics.

  1. Move the victim to a cool place: Help the person lie down in a cool environment, such as a room with air conditioning or a shaded area.
  2. Remove excess clothing: Take off any unnecessary clothing to expose more of their skin to the air.
  3. Cool their skin: Use available resources like a cool, damp sponge or cloth, cold packs placed on the neck and armpits, or wrap them in a damp, cool sheet to lower their body temperature.
  4. Assist with air circulation: Fan their skin gently while it is moist, as this aids in the evaporation of water and facilitates the body’s cooling process.
  5. Encourage fluid intake: Offer them fluids to drink, preferably water, fruit juice, or a rehydration drink like a sports drink with electrolytes.
  6. Avoid certain medications: Refrain from giving them aspirin or paracetamol, as these medications will not effectively reduce their elevated temperature and may be harmful.

Once in the hospital, doctors usually diagnose heat stroke via a physical examination of symptoms. However, they may conduct additional tests to confirm or rule out any other causes, such as organ damage. These tests include examining muscle or kidney function, blood analyses for gas or electrolyte levels, and imaging tests to check for internal damage.

What are the symptoms of heat stroke?

Symptoms of heat stroke include a variety of manifestations that reflect the body’s inability to effectively regulate its own temperature. Below are the nineteen common heat stroke symptoms.

  • High temperature: Body temperatures above 40°C/104°F overwhelm the body’s thermoregulatory system.
  • Extreme thirst: Heat stroke causes the body to sweat profusely in an effort to cool itself, leading to rapid dehydration and profound thirst.
  • Fatigue: A state of physical and mental exhaustion which manifests differently depending on age.
  • Muscle weakness: A sudden, noticeable decrease in physical strength.
  • Cramps in extremities: A severe symptom of dehydration characterized by contractions, tremors, weakness, and impaired mobility.
  • Altered mental state: Characterized by abnormal behaviour and/or cognitive impairment.
  • Dizziness: A feeling of faintness or instability that can lead to dangerous falls.
  • Headache: A result of disruptions to hydration and electrolyte balance.
  • Nausea and vomiting: A severe heat stroke symptom stemming from disruption of digestive processes.
  • Stomach cramps: A result of heat-related disruption to the digestive tract’s blood flow and oxygen supply.
  • Diarrhoea: A rare but serious symptom of digestive disruption that expedites dehydration and electrolyte imbalance.
  • Malaise: A general feeling of unwellness that includes nausea, dizziness, discomfort, and weakness.
  • Clammy skin: An important early symptom of heatstroke where the body’s sweat evaporates off the skin.
  • Excessive sweating: Another early symptom of heat stroke that indicates the body is working hard to compensate for excessive heat exposure.
  • Lack of sweat: An extremely dangerous later-stage symptom of heat stroke that signals depletion of bodily hydration for use in sweating.
  • Heat rash: The result of blocked sweat ducts, leading to small, red bumps or blisters on the skin.
  • Rapid heartbeat: Excess heat makes the heart work harder to supply blood and oxygen to the body, characterized by 100+ bpm heart rates.
  • Fast breathing: A dangerous symptom in which blood vessels dilate to dissipate excess heat, forcing a higher respiration rate to compensate for reduced oxygen.
  • Loss of consciousness: A late-stage symptom of heat stroke resulting from the lack of oxygen due to constricted blood vessels.

Knowing these symptoms and their development risk is crucial in identifying and responding promptly to heat stroke. Seek immediate medical attention to prevent complications if you observe any heat stroke symptoms.

High body temperature

A high body temperature (40°C/104°F or higher) is one of the defining characteristics of heat stroke. The body’s thermoregulatory system becomes overwhelmed when exposed to extreme heat or engaged in strenuous physical activity in hot environments, leading to a rapid increase in core body temperature. A body temperature above 40°C/104°F may lead to an increased heart rate and blood pressure, an altered mental state, confusion, and seizures.

It’s vital to recognise heat stroke early in order to treat it appropriately and ensure the greatest chances of survival. Signs of high temperature may be difficult to observe without a thermometer. However, below are the telltale signs of heat-induced high body temperature in adults, children, and pets.

  • In adults: Look for symptoms such as flushed skin that’s hot to the touch, excessive sweating, and a feeling of extreme heat.
  • In children: Pay attention to signs such as flushed or red skin, hot to the touch, excessive thirst, as well as lethargy and rapid breathing. Children may not be able to communicate their heat-related discomfort effectively, so it’s important to be vigilant during hot weather.
  • In pets: Watch for signs of distress, including excessive panting, bright red or pale gums, drooling, weakness, and vomiting. Pets may seek cool surfaces or shade and exhibit unsteadiness or collapse.

Seek emergency medical care right away if you or someone you know displays any of the aforementioned while subjected to a hot environment.

Extreme thirst

Extreme thirst is a common heat stroke symptom that signals the body’s immediate need for hydration. Dehydration generally occurs during a heat stroke, as the body loses excessive amounts of fluid through sweating. The body strives to restock the fluids lost to sweat, and heat stroke victims experience this process as extreme thirst.

Below are the different ways feelings of extreme thirst manifest in adults, children, and pets.

  • In adults: In adults, extreme thirst may present itself as a persistent feeling of dry mouth, throat, and lips.
  • In children: Children may exhibit signs of increased fussiness, irritability, and persistent requests for drinks.
  • In pets: Pet owners should look out for signs like excessive panting, searching for water sources, or attempting to drink from unusual places.

Request emergency medical services right away if you experience or witness extreme thirst caused by a heat stroke. Don’t hesitate to hydrate yourself or the victim while awaiting medical care.


Fatigue is a state of overwhelming physical and mental exhaustion and is one of the more common signs of heatstroke. Fatigue is characterised by a persistent lack of energy, reduced motivation, and an overall feeling of weariness. Fatigue is a dangerous symptom for those suffering from heat stroke, as it could lead to the patient falling asleep, passing out, or becoming delirious. Signs of fatigue can disappear within a few days or weeks in less severe cases of heatstroke and with adequate rest and hydration. However, in some cases, fatigue can linger for several weeks or months even after prompt treatment.

Early recognition of fatigue in yourself or a loved one helps diagnose and treat heat stroke quickly. Be alert for signs of persistent exhaustion, a severe lack of energy, and decreased physical and mental performance that doesn’t improve even after rest. However, note that fatigue can manifest differently between adults, children, the elderly, and pets during a heat stroke. In adults, fatigue appears as a feeling of overwhelming tiredness, reduced energy, and trouble concentrating or performing tasks. Children might show fatigue through excessive sleepiness, irritability, lethargy, or indifference to activities that might generally stimulate them. Fatigue often causes confusion, disorientation, and weakness in older patients with heatstroke. Pets exhibit fatigue by being less active, struggling to walk or stand, seeming detached or disinterested, or seeking cooler spots to lie down. Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) should take extra care in hot conditions, such as staying well hydrated, seeking out shade, and listening to their body’s needs for rest and relief from the heat. However, heatstroke itself is not directly linked to causing ME/CFS.

Muscle weakness

Muscle weakness is a common symptom associated with heatstroke. Heat stroke-related muscle weakness is characterised by a significant decline in muscle strength. Muscle weakness may affect both the upper and lower body, thus causing difficulties in performing even the simplest of tasks.

A heat stroke episode may lead victims to experience varying degrees of muscle weakness, depending on factors such as age, virility, and overall health. Below is a list of the different manifestations of heat-related muscle weakness in people of varying age groups and in pets.

  • In adults: In adults, muscle weakness usually manifests as a general feeling of bodily fatigue and difficulty in performing physical activities that are usually manageable.
  • In children: Children may exhibit muscle weakness through displaying fatigue or the inability to engage in physical play.
  • In the elderly: In the elderly, muscle weakness during heat stroke can contribute to balance problems, unsteadiness, and difficulty when standing or walking.
  • In pets: Pets may display signs of muscle weakness by being less active, struggling to move, or appearing lethargic.

In some cases, heat stroke-related muscle weakness is a sign of a serious medical emergency. Intense physical exertion in hot conditions can lead to the onset of exertional heatstroke (EHS) and cause rhabdomyolysis (Rhabdo). Rhabdo is a condition characterised by muscle breakdown due to heat stress or overexertion, and the consequent release of myoglobin into the bloodstream. Rhabdomyolysis strains the kidneys and may potentially lead to kidney damage if not promptly treated. Therefore, it’s crucial to prevent conditions like rhabdomyolysis from developing when exposed to extreme heat. Avoid strenuous activities in high temperatures, and seek immediate medical attention if you experience muscle weakness while subjected to heat.

Cramps in extremities

Cramps in extremities (legs, arms, feet, and hands) are severe symptoms of heat stroke caused by overheating and dehydration. The high body temperature that accompanies heat strokes results in excessive sweating and loss of fluids. The resulting dehydration disrupts the body’s balance of electrolytes, including sodium, potassium, and calcium, which are all essential for proper muscle function. This electrolyte imbalance triggers muscle cramps in the extremities.

Heat cramp symptoms include painful muscle contractions, sweating, irritability, restlessness, muscle tremors, difficulty moving, and vocalisation in pets and young children. The occurrence of muscle cramps in the extremities of a person subjected to extreme heat is an urgent sign that the victim requires immediate medical care.

Altered mental state

An altered mental state may develop as a result of the body’s response to excessive heat and dehydration. An altered mental state is a condition that’s characterised by changes in cognitive function and abnormal behaviours that occur due to the body’s response to hyperthermia. This state is caused primarily by the profound impact of the elevated body temperature on the brain’s neural pathways. A body temperature of 40°c (104°f) leads to changes in cognition and behaviour by disrupting the normal functioning of the brain in three ways. Firstly, the elevated body temperature associated with heat stroke causes cellular damage and inflammation in the brain, disturbing the delicate balance of neurotransmitters that are responsible for communication between neurons. This disruption in neurotransmitter function results in altered mental states, including confusion, disorientation, irritability, agitation, and even loss of consciousness. Secondly, excessively high body temperature may cause the brain to accumulate unwanted proteins and ions, leading to an inflammatory response and disruption of the brain’s normal functioning. Thirdly, heat exposure and the resulting dehydration cause electrolyte imbalances, including low levels of sodium and potassium. These imbalances further contribute to altered mental states. Neurons depend heavily on electrolytes to function properly, and disturbances in their levels interfere with electrical signals sent between different parts of the brain.

Below is a list of the typical heat stroke-related altered mental state manifestations in adults, children, and pets.

  • In adults: Confusion, disorientation, difficulty concentrating, and changes in behaviour are often seen in adults suffering from heat stroke.
  • In children: Children experiencing a heat stroke may become irritable, lethargic, or excessively cranky.
  • In pets: In pets, heat stroke may manifest in restlessness, agitation, confusion, disorientation, and unusual vocalisation.

Long-term neurological complications of untreated heat stroke vary in severity and may include cognitive impairment, neurological damage, organ dysfunction, and behavioural and emotional changes. The duration of these symptoms ranges based on the factors such as the individual’s health condition and the severity of the heat stroke episode.


Dizziness (known as syncope) often occurs as a response to excessive heat exposure and dehydration. Dizziness refers to a sensation of lightheadedness, unsteadiness, or feeling faint. Heat-stroke-related dizziness is caused by the impact of elevated body temperature on the cardiovascular system and fluid balance. Physical exertion and a high body temperature lead the body to dispel heat through the dilation of blood vessels. Dilated blood vessels compel the heart to work harder to ensure proper circulation. The heart (like any muscle) has its limits and becomes exhausted when overworked. The cardiovascular system thus becomes disrupted in the advanced stages of heat stroke, and heart rate and blood flow slow down. Insufficient blood supply to the brain leads to lightheadedness, dizziness, and fainting.

Heat stroke-induced dizziness exhibits different symptoms in adults, children, and pets. Adults experience lightheadedness, vertigo, and unsteadiness, while children may show imbalance, clumsiness, and wobbly walking. Pets suffering from heat stroke may experience disorientation, stumbling, or difficulty coordinating. Symptoms that accompany heat-related dizziness generally include nausea, a weak or rapid pulse, and a spinning or unsteady sensation.

Dizziness during heat stroke signifies a medical emergency that requires immediate attention for two reasons. Firstly, heat-induced dizziness may result in dangerous falls and injuries. Secondly, untreated heat stroke-related dizziness may lead to prolonged or recurring episodes and even death. It is important to treat heat stroke as soon as dizziness presents as a symptom, and rapid cooling and rehydration are able to prevent dizziness and loss of consciousness.


Headache is a common heat stroke symptom caused by dehydration. Heat stroke causes dehydration as the elevated body temperatures disrupt the body’s fluid and electrolyte balance, thus reducing blood volume and oxygen delivery to the brain. Severe headaches caused by dehydration are often accompanied by other heat stroke symptoms, such as dizziness and fatigue. Maintaining proper hydration levels during hot weather is crucial in preventing heat stroke and related symptoms, such as headaches.

A heat stroke triggers the following headache types in adults and children.

  • In adults: Adults may undergo intense pain, sensitivity to light and sound, as well as nausea or vomiting.
  • In children: Children may tend to be restless or irritable, while pets may display more subtle symptoms like excessive panting or unwillingness to move.

Headaches experienced during heatstroke vary in intensity and duration. Some individuals may only experience mild discomfort, while others may suffer from debilitating pain. Prompt recognition and effective management of a heat stroke are essential to prevent the worsening of headaches and the onset of other serious heat stroke symptoms.

Seek immediate medical attention if you or someone you know has persistent headaches, particularly in conjunction with other heatstroke symptoms, such as high body temperature, nausea, and dizziness.

Nausea and vomiting

Heat-induced nausea and vomiting are severe heat stroke symptoms that require immediate medical attention. Nausea occurs when excessive heat interrupts the digestive system’s normal functioning, leading to dehydration and electrolyte imbalances. Dehydration slows down the digestion process, causing food to stay in the stomach for longer periods, which leads to feelings of abdominal discomfort and nausea.

Heat stroke-induced nausea presents itself in the following ways in adults, children, and pets.

  • In adults: Symptoms in adults include weakness, sweating, a buildup of saliva, and an urge to vomit.
  • In children: Children may become pale, lose their appetite, and complain of a stomach ache.
  • In pets: Pets may drool excessively, vomit, appear uncomfortable, and show disinterest in food or water.

Note that relieving the symptoms above is best done by addressing the underlying cause (heat stroke), not by attempting to control nausea through medications. However, the aforementioned symptoms often overlap with other conditions, so it’s important to consult with a healthcare professional for a proper evaluation and diagnosis of these manifestations after heat exposure.

Stomach cramps

Stomach cramps are a heat stroke symptom that indicates heat-related disruptions to a person’s digestive system. The dehydration and overheating that occur during a heat stroke cause the blood vessels in the digestive system to constrict, resulting in decreased blood flow and oxygen supply to the gastrointestinal tract. Reduced oxygen supply to the gastrointestinal tract results in stomach cramps, abdominal pain, bloating, and discomfort, and may cause oxidative stress in intestinal cells, affecting both the cells’ survival and their function.

The severity of stomach cramps varies, ranging from mild discomfort to intense pain. Regardless of severity, it’s crucial to recognise stomach cramps as a heat stroke symptom in individuals who are subjected to prolonged periods of excessively high temperatures and overexertion. Seek immediate medical help if you or someone you know has developed stomach cramps while enduring high ambient temperatures.


Diarrhoea is a possible (albeit rare) heat stroke symptom. The dehydration and overheating that accompany heat stroke cause electrolyte imbalances and nutrient depletion in the victim’s body, which in turn affect the neurological, cardiovascular, and digestive systems. The impaired function of the digestive tract may manifest as changes in bowel movements and diarrhoea.

It is essential to take note of heat stroke symptoms such as diarrhoea and seek medical attention immediately when such symptoms occur. Rehydration and electrolyte replacement should be your top priority after seeking professional medical attention for someone with heat-induced diarrhoea.


Malaise is a common heat stroke symptom characterised by discomfort, nausea, vomiting, dizziness, and weakness that stem from dehydration and exposure to excessive heat. Heat stroke causes malaise as the elevated body temperature impacts various organs, including the brain, heart, and gastrointestinal system. Dehydration is a common consequence of heat stroke, and it disrupts the balance of fluids and essential minerals, leading to decreased blood volume and impaired circulation. Dehydration causes tissues and organs to receive less oxygen and nutrients, leading to a general feeling of fatigue, weakness and physical strain.

Below are the different ways in which heat stroke-related malaise presents differently in adults, children, and pets.

  • In adults: Adults may experience fatigue, weakness, and discomfort along with a lack of motivation and energy.
  • In children: Children may become irritable, lethargic, and lack appetite.
  • In pets: Pets may become restless, refuse food or water, and exhibit unusual behaviour.

It’s important to closely monitor these signs of malaise as they indicate the severity of heat stroke. However, note that heat stroke is always a medical emergency, and you should seek prompt medical attention if you or someone you know develop malaise while subjected to excessive heat.

Clammy skin

Clammy skin is a significant initial symptom of heat stroke. This chilly and moist sensation is a result of your sympathetic nervous system (mechanism responsible for the “fight-or-flight” response) triggering the production of sweat. Sweat evaporates from your skin, thus cooling the body and creating a characteristic clammy feeling. Clammy skin itself does not pose an immediate danger, but people exposed to excessive heat and overexertion should treat it as a harbinger of heat stroke.

Act swiftly if you or someone you know experiences clammy skin along with other heat stroke symptoms. Prompt treatment is critical in preventing the progression of heat stroke and its most serious consequences, such as organ damage, coma, and death.

Excessive sweating

Excessive sweating is an early symptom of heat stroke onset. Prolonged heat exposure and physical overexertion cause the body temperature to rise considerably, and the body responds by producing great quantities of sweat to release the excess heat. Profuse sweating in turn leads to dehydration and the consequent disruption to neurological, cardiovascular, and digestive processes, at which point the victim experiences a full-blown heat stroke. Heat stroke-related sweating ceases once the victim’s temperature-regulating mechanism shuts down and the condition becomes life-threatening. It’s vital to recognize profuse sweating as a sign of an impending heat stroke and immediately cool the body down before the heat stroke progresses.

Lack of sweat

Lack of sweat (also known as “anhidrosis” and “hypohidrosis”) is a dangerous late-stage heat stroke symptom that emerges when dehydration disrupts the body’s ability to produce sweat. Dehydration generally develops in heat stroke victims as their bodies sweat profusely in an attempt to cool off. Excessive sweating drains the body of fluids, and the body responds by prioritising the remaining fluids to keep vital organs functioning properly. Sweat glands cease to produce sweat as a result, and the victim’s body is left without a means to cool itself, causing a rapid rise in temperature. Heat stroke symptoms worsen as body temperature continues to climb, and the risk of organ failure, coma, and death increases.

Heat stroke-induced anhidrosis is an extremely dangerous sign that means that the victim requires emergency medical care.

Heat rash

Heat rash (also known as “prickly heat” or “miliaria”) is a possible heat stroke symptom that involves the formation of small, red bumps or blisters on the victim’s skin. Heat rash develops when a person’s sweat ducts become blocked during excessive perspiration, thus trapping sweat beneath the skin. The trapped sweat causes the heat rash. Heat stroke-induced miliaria often appears in areas where sweat accumulates, such as the neck, chest, groin, or skin folds.

Heat rash itself is not a severe condition, but it may indicate a heat stroke in someone who is subjected to extreme heat or overexertion. Seek immediate medical attention if you or someone you know develops a heat rash during exposure to extreme heat. Heat stroke is a medical emergency and requires prompt treatment to prevent life-threatening complications.

Rapid heartbeat

Heat stroke commonly causes rapid heartbeat (known as “tachycardia”), which is characterised by a heart rate exceeding 100 beats per minute. Increased heart rates occur when the cardiovascular system is forced to work harder as a result of elevated body temperatures.

Recognising rapid heartbeat symptoms in adults, children, and pets is crucial for prompt intervention during a heat stroke. Below are the different ways rapid heartbeat may manifest in adults, children, and pets.

  • In adults: Adults may experience palpitations, a pounding or racing sensation in the chest, and a noticeably rapid pulse.
  • In children: Children may show signs of dizziness, restlessness, or weakness alongside a racing heartbeat.
  • In pets: Pets may display rapid breathing, panting, and an increased heart rate.

Heat stroke-induced rapid heartbeat can lead to severe complications if left untreated. The cardiovascular system can be further strained, potentially resulting in cardiac arrhythmias, heart failure, or even cardiac arrest. Immediate medical attention is necessary to prevent the progression of these complications if someone develops a rapid heartbeat in an extremely hot environment.

Fast breathing

Fast breathing (known as “tachypnea”) is a dangerous symptom of heat stroke and heat exhaustion. Exposure to extreme heat causes the body to increase the breathing rate. The respiration rate increases to maintain vital oxygen levels, as blood vessels dilate to dissipate heat and blood flow to major organs decreases. The heightened respiratory effort strains the cardiovascular system, resulting in respiratory distress and even respiratory failure.

Recognising tachypnea is crucial in identifying heat stroke and seeking emergency medical help. Call for medical assistance without delay if you or someone you know develops rapid or shallow breathing while enduring high ambient temperatures or undergoing overexertion.

Loss of consciousness

Loss of consciousness (known as “syncope”) is a severe symptom associated with heat stroke. Temporary loss of consciousness happens when overheating dilates the blood vessels, thus reducing blood flow to the brain. Reduced blood and oxygen levels in the cerebral cortex disrupt the neural activity that keeps a person conscious, and the person faints.

Take any loss of consciousness in a hot environment seriously, and follow the six steps below to assist the victim.

  1. Call for emergency medical assistance: Dial 999 and inform the dispatcher about the situation.
  2. Move the affected person to a cool area: Place the person in a shaded or air-conditioned room away from direct sunlight and heat if it is safe to do so.
  3. Check their airway and breathing: Check whether the victim’s airway is clear and check for signs of breathing. If the person is not breathing, initiate cardiopulmonary resuscitation (CPR) if trained to do so.
  4. Loosen tight clothing: Clothing that is tight or constricting should be removed in order to facilitate better air circulation.
  5. Apply cool compresses: Use cool, damp cloths or ice packs on the person’s forehead, neck, groin and armpits to lower their body temperature.
  6. Monitor vital signs: As you wait for the paramedics, keep an eye on their pulse, breathing, and level of responsiveness.
Heat stroke symptoms, prevention, and treatment

How to prevent heat stroke?

It’s crucial to take proactive measures when in hot, humid conditions to prevent heat stroke. Below are five effective strategies for preventing heat stroke regardless of your location.

  • Stay hydrated: Drink a lot of fluids, particularly water, even if you’re not thirsty. However, take care to avoid overhydration, which may affect your electrolyte balance.
  • Avoid strenuous activity: Don’t overexert yourself during peak heat hours, and ensure to take frequent breaks in cooler, shaded areas.
  • Dress in loose clothing: Dress comfortably in loose, breathable clothing that allows consistent air circulation around the body.
  • Protect yourself from the sun: Protect yourself from the sun by wearing a hat, and sunglasses, and applying sunscreen to prevent sunburn.
  • Be mindful of vulnerable individuals: Be mindful of individuals who are vulnerable to heat stroke, like the elderly, children, those with chronic health conditions, and those living alone.

The strategies above help avert heat stroke in most settings, but you may have to adopt additional methods depending on whether you’re at home, outdoors, in transit, or at work. Likewise, heat stroke prevention methods differ depending on the age group, since children and the elderly are more susceptible to the condition than healthy adults.

How to prevent heat stroke at home?

Prevent heat stroke at home using the five strategies below.

  • Keep the home cool and ventilated: Keep your indoor environment cool using air conditioning or fans. Open your windows during the coolest part of the day (night and morning), and close them before the outdoor air heats up in the afternoon.
  • Stay hydrated: Drink plenty of fluids, but avoid consuming too much water. Excessive water consumption causes an electrolyte imbalance, which may exacerbate the effects of heat. On the other hand, sports drinks replenish the electrolytes in your body during periods of intense heat.
  • Wear comfortable clothing: Wearing lightweight clothing helps you stay comfortable in a hot indoor environment. Breathable fabrics such as cotton, linen, and silk allow your body to breathe and do not trap heat.
  • Use comfortable bedding: Look for bedding made from breathable and moisture-wicking fabrics like cotton or linen, as these materials allow for better airflow and help keep you cool. Consider using lightweight blankets or sheets to avoid excessive heat retention at night to keep your body temperature down. Some people find that cooling bedding items, like gel-infused mattress toppers and cooling pillows, help regulate the body temperature when it’s hot indoors.
  • Stay in touch with friends or family: Keep in touch with your loved ones and have them visit if you live alone. A visiting friend or family member may be able to assist you with daily tasks (so that you don’t overexert yourself) and call for medical assistance if they recognize signs of heat stroke.

How to prevent heat stroke outdoors?

Employ the five methods below to prevent heat stroke outdoors.

  • Avoid direct sunlight: Avoid prolonged exposure to direct sunlight, especially at the hottest part of the day. Seek shade where possible and wear summer hats with wide brims to increase your protection from solar radiation. Lowering exposure to the sun is an effective way to prevent sunburn, which compromises your body’s thermoregulatory abilities and potentially leads to sunstroke. Minimising direct sun exposure helps you significantly reduce the chances of developing heat stroke.
  • Stay hydrated: Drink plenty of water and sports drinks, especially when temperatures are at their highest. Stay away from caffeinated and alcoholic beverages, as these contribute to dehydration.
  • Know where to cool off: Familiarise yourself with the nearest air-conditioned public spaces, such as shopping centres, libraries, or civic buildings. Knowing where to go to cool off helps you save precious time when your body is overheated and you’re in desperate need of air-conditioned space.
  • Avoid overexertion: Stay away from strenuous tasks, as these tend to hasten the rise of your body temperature and contribute to dehydration.
  • Wear comfortable clothing: Dress in loose-fitting clothing made from breathable materials, such as cotton and linen, as these do not trap heat next to your body the way synthetic fabrics do.

How to prevent heat stroke while in transit?

Follow the three strategies below to prevent heat stroke while in transit.

  • Ensure proper cooling and ventilation: Use your car’s air conditioning or open windows to allow for adequate airflow. Public transit is typically air-conditioned, but be sure to open the nearby windows if you’re in a vehicle without a working A/C.
  • Make rest stops: Take rest breaks during long journeys and carry plenty of water to keep yourself hydrated. Frequent breaks and hydration are particularly important when travelling in foreign countries with hot climates to which you are not accustomed.
  • Never leave children or pets unattended in parked cars: Temperatures quickly rise in small, poorly ventilated areas such as cars. Hot car deaths happen every year because parents and pet owners leave their kids and furry friends unattended in parked vehicles. Do not leave children or pets in locked, parked cars, even if the day does not seem to be particularly hot.

How to prevent heat stroke at work?

Prevent heat stroke at work by following the five methods below.

  • Cool or ventilate your workplace: Get a desk fan if there is no air conditioner at your workplace. Alternatively, open the doors and windows to produce a draught in the space.
  • Stay hydrated: Drink lots of fluids but avoid overhydration that could disrupt the balance of electrolytes.
  • Take breaks when possible: Take breaks whenever you’re able to. Find time to sit or lay down and relax if your job demands heavy physical tasks. Conversely, find time to stretch and walk around if you’re sitting for long periods behind your work desk.
  • Learn relevant workplace policies: Your employer may have in place policies that address work in hazardous environments, such as extreme heat. Familiarise yourself with these guidelines, as they likely outline protective measures, as well as your rights and responsibilities when working in a hazardous environment.
  • Speak with your supervisor: Let your supervisor know if you’re vulnerable to heat stroke, and they may be able to move you into a cooler space, allow you to take breaks more frequently, or recommend other measures to protect you from extreme heat.

How to protect children from heat stroke?

Below are the five strategies you should follow to protect children from heat stroke.

  • Minimise heat exposure: Limit your children’s outdoor activities during peak hours, never leave them unattended in hot cars, and try to create a cool, ventilated environment for them at home.
  • Keep children hydrated: Pay close attention to how much liquids your children drink and adjust their consumption accordingly. However, take care not to overhydrate them.
  • Pick suitable clothes: Dress your kids in loose, breathable clothing, and make sure they wear headdress when outdoors.
  • Educate your children about heat: Your children should be aware of the dangers and consequences of extreme heat, as this knowledge might push them to be proactive in protecting themselves from the effects of hot weather.
  • Monitor their well-being: Seek medical attention if your child shows heat-related illness symptoms.

How to protect the elderly from heat stroke?

Take the following three actions to protect the elderly from heat stroke.

  • Visit often: It is crucial that family members, neighbours, caregivers, and medical professionals keep a close eye on the elderly when temperatures soar. Check on the elderly often during heat waves, particularly if they live alone and do not have an air conditioner installed at home. Older people are more vulnerable to the effects of extreme heat, and their heat stroke symptoms often progress quickly. Visiting the elderly during a heat event allows you to monitor their well-being, help them stay cool and hydrated, and call emergency services if needed.
  • Find a place to cool off: Older people are more susceptible to heat events, so consider taking your elderly loved ones to an air-conditioned space if they don’t have A/C at home. Waiting out the hottest hours of the day in an air-conditioned environment protects them from the most intense, potentially dangerous heat.
  • Engage in light exercise: Encourage the elderly to engage in light exercise during the cooler parts of the day. Doing so keeps them active without exposing them to the risks of extreme outdoor temperatures.

How to protect pets from heat stroke?

Take the five actions below to protect pets from heatstroke.

  • Keep pets hydrated: Give your pets plenty of fresh, cool water.
  • Don’t leave pets in cars: Do not leave your pets in enclosed spaces such as hot cars or poorly ventilated rooms.
  • Give pets a place to cool off: Provide them access to shaded areas with good air circulation. Cooling accessories, such as pet cooling mats or wet towels help them regulate their body temperature. Frozen treats made with pet-safe ingredients are another way to cool down.
  • Limit outdoor time during hot hours: Limit your pets’ physical activity during the hottest parts of the day and opt for shorter walks or play sessions. Walk your pets earlier in the morning and later in the evening, when the heat from the sun is weaker. Protect pets’ paws from hot surfaces by avoiding scorching pavements and opting instead for grassy or shaded areas.

How to treat heat stroke?

Do not attempt to treat heat stroke yourself: seek immediate, professional medical attention. Heat stroke can be fatal without medical intervention, therefore always call 999 at the first heat stroke symptoms. While you wait for the paramedics, take the following five steps to assist the heat stroke victim.

  1. Take the victim to a cool place: Cool the person down by taking them out of the heat and to a cooler, preferably shaded place.
  2. Remove excess clothing: Take off any heavy or constricting garments so that the heat trapped beneath the victim’s clothes is able to escape.
  3. Rehydrate the victim: Encourage the victim to drink plenty of fluids, preferably those that replenish electrolytes.
  4. Cool them off: Apply cool compresses or ice packs to the groin, armpits and neck if possible.
  5. Monitor the victim: Continue to monitor the heat stroke victim closely as you wait for paramedics.

How to treat heat stroke when travelling?

Follow the six steps below to treat heat stroke when travelling.

  1. Stop the vehicle and disembark the victim: The first priority is to find a safe place to stop the vehicle or disembark from public transport.
  2. Call emergency services: Dial 999 and advise the dispatcher of the situation and state your location.
  3. Move the victim to a cool spot: Move the person experiencing heat stroke to a safe, cool and shaded area away from direct sunlight.
  4. Cool the victim down: Make an effort to cool the person down by applying cool water or ice packs to their skin. Try to obtain cold wet towels from nearby businesses if necessary.
  5. Encourage rehydration: Get the victim to drink cool water or a sports drink if they are conscious and able to swallow.
  6. Monitor the victim: Keep an eye on the person experiencing heat stroke until emergency medical services arrive on the scene and take over. Check for vital signs if the person loses consciousness and perform CPR if necessary.

How to treat heat stroke in pets?

Get immediate veterinary care to treat heat stroke in pets. Pre-cool the vehicle in which you plan to transport the pet and lay down some wet towels on the seat before placing the pet onto it. Spray the pet with water if possible before you commence the journey to help it cool off as much as possible.