Heat-related health problems

Heat kills more people than any other natural disaster. As the climate warms, hot days and intense heatwaves are becoming more common. It is more important than ever to know the risks of heat and how to protect yourself and others.

Extreme heat can affect anybody#

Heat-related health problems happen when the body cannot cool down well enough to keep a healthy temperature, or becomes dehydrated through sweating. Heat can cause serious and potentially fatal conditions such as heat exhaustion and heatstroke, trigger sudden events like heart attack or stroke, or worsen existing medical conditions such as kidney or lung disease.

Anyone can be affected, but those at higher risk include:

• People over the age of 65
• Babies and young children
• Pregnant women
• People with acute or chronic health problems, such as heart disease, kidney disease, diabetes or mental illness
• People who work or exercise outdoors
• People taking certain medications, including diuretics (fluid tablets), beta-blockers, drugs with anticholinergic properties and central nervous system stimulants
• People who are socially isolated or living alone, as there may be no one to check on them during extreme heat
• People with limited ways to keep cool, such as those in buildings that heat up easily or people experiencing homelessness

How heat harms the body#

During hot weather, the body works to prevent overheating by sweating and by redirecting blood flow to the skin. People can also help themselves by staying in cool places and drinking more water than usual. Heat-related health problems occur when these protective changes, together with the actions people take, are not enough to avoid overheating or dehydration, and organ systems begin to fail.

This can happen through several pathways:

• A large rise in body temperature from a build-up of heat leads to conditions such as heat exhaustion and, eventually, heatstroke, which is a medical emergency.
• Redirecting blood flow to the skin means the heart has to work harder than normal. This extra strain can trigger problems in people with existing heart conditions, such as a heart attack.
• Increased sweating can lead to dehydration if lost fluid is not replaced. Dehydration can cause weakness and fainting, lead to kidney problems and worsen other medical conditions.

It is important to know the signs and symptoms of heat-related health problems and how to respond. Seek medical help immediately if someone shows signs of heat exhaustion, heatstroke or another health emergency.

Dehydration#

Dehydration occurs when the body does not have enough fluid to carry out its normal functions. Symptoms include thirst, dry mouth, passing less urine than usual, dark or strong-smelling urine, dizziness or headache, and irritability or difficulty thinking clearly.

First aid for dehydration due to heat:

• Move to a cool area.
• Drink plenty of fluids.
• Remove unnecessary clothing.
• Cool down by wetting the skin with cool water.
• See a doctor if there is no improvement or you are concerned.

Heat exhaustion#

Heat exhaustion is a serious condition that can progress to heatstroke. It can occur when the core body temperature rises to about 38-39°C (100-102°F). Signs and symptoms include heavy sweating, pale skin, muscle cramps, weakness, dizziness, headache, nausea, vomiting, fainting and a rapid pulse.

First aid for heat exhaustion:

• Get the person to a cool area and lay them down.
• Remove excess clothing, including shoes and socks.
• Cool the person down: wet their skin with cool water, fan continuously, apply a cool, damp sponge or cloth, or place ice packs or crushed ice in a damp towel on the neck, groin or armpits.
• If they are able, have them take a cool shower or bath.
• Encourage frequent sips of cool water.
• Seek medical advice, or arrange transport to a doctor or emergency department. Call your local emergency number (for example 911 in the US and Canada, 112 across the EU and many countries, 999 in the UK, or 000 in Australia) for an ambulance if the person is not improving or you think they could have heatstroke.

Heatstroke#

Heatstroke can occur when the core body temperature rises above 40°C (104°F) and blood flow to internal organs is restricted. Many organs can be damaged, and the body temperature must be lowered quickly. Heatstroke may look similar to heat exhaustion, but the skin may be dry with no sweating, and the person may appear confused or agitated.

Signs and symptoms include a very high body temperature, confusion or agitation, loss of consciousness, profuse sweating or hot dry skin, muscle twitching or seizures, rapid breathing and a rapid pulse.

Heatstroke is a medical emergency and requires urgent attention:

• Call your local emergency number (for example 911 in the US and Canada, 112 across the EU and many countries, 999 in the UK, or 000 in Australia) immediately for an ambulance.
• While waiting for help, get the person to a cool, shady area and lay them down.
• Have someone stay with the person.
• Remove excess clothing, including shoes and socks.
• Cool the person as quickly as possible: wet their skin with cool water, fan continuously, apply a cool, damp sponge or cloth, or place ice packs or crushed ice in a damp towel on the neck, groin or armpits.
• Give cool water to drink only if the person is fully conscious and able to swallow.
• Position an unconscious person on their side and check they are breathing normally. Be ready to give CPR if needed.
• If medical attention is delayed, follow further instructions from emergency, ambulance or hospital staff while waiting for the ambulance.

Heat cramps#

Heat cramps are muscle pains or spasms, usually in the abdomen, arms or legs. They may occur after strenuous activity in a hot environment, when the body becomes depleted of salt and water. Heat cramps can also be a symptom of heat exhaustion.

First aid for heat cramps:

• Rest in a cool place.
• Increase fluid intake.
• Rest a few hours before returning to activity.
• Seek medical help if there is no improvement, the person is unwell, or you are concerned.

Heat rash#

Heat rash, also known as prickly heat, is an itchy skin irritation caused by excessive sweating. It can occur at any age but is most common in babies and young children. It tends to appear on the neck, upper chest, waistline, groin, under the breasts, and in skin folds and armpits. Symptoms include redness, mild swelling and a cluster of small red spots in the affected area, with itching and a prickling sensation. These can last for several days.

Heat rash normally goes away without treatment. To prevent it and help it clear faster:

• Move to a cooler, well-ventilated and less humid environment to cool down and stop sweating.
• Keep the affected area dry.
• Wear loose cotton clothing to help prevent overheating, and avoid scratchy fabrics that irritate the skin.
• A pharmacy can recommend treatments to ease itching and inflammation.
• If symptoms do not improve, see your doctor.

Preventing heat-related health problems#

Take steps to protect yourself and your loved ones from heat-related health problems. Keep cool, stay hydrated, plan ahead and check in with others during hot weather.

Key points#

• It is more important than ever to know the risks of heat and how to protect yourself and others.
• During hot weather, the body works to prevent overheating by sweating and redirecting blood flow to the skin.
• Dehydration can cause weakness and fainting, lead to kidney problems and worsen other medical conditions.
• Know the signs and symptoms of heat-related health problems and how to respond.
• Symptoms vary according to the type of health problem.

Where to get help#