Heat-related illnesses occur when the body is unable to cool itself by sweating, leading to a buildup of heat in the body (hyperthermia). Similar to the way extreme cold can lead to hypothermia, exposure to high temperatures over a prolonged period of time can be deadly. According to the Centers for Disease Control and Prevention (CDC), heat-related illnesses claim about 300 lives in the United States each year.
There are several types of heat illness, including heat stroke, heat exhaustion, heat cramps, heat rash and sunburn. Of these, heat stroke and heat exhaustion are the most common (with the exception of sunburn) and the most dangerous. Heat stroke can be fatal, and heat exhaustion can lead to heat stroke if it goes untreated. Signs and symptoms of these two conditions are quite different and learning to recognize them can save lives.
Factors that increase a person’s risk of developing a heat-related illness include:
Hot weather. Heat waves, especially in areas that do not regularly experience hot weather, are the most obvious and most common risk factor for heat-related illnesses.
Age (the elderly and young children are at higher risk)
Weight (overweight and obese people are at higher risk)
Mental illness (people who are less likely to take basic precautions or are taking medications that increase their risk)
Medications that increase a person’s sensitivity to the sun or heat (e.g., ACE inhibitors, diuretics, psychotropics)
Existing fever or sunburn, dehydration, or alcohol use
Some illegal drugs (e.g., cocaine)
Tips for preventing heat-related illness include:
Drinking plenty of fluids (avoiding caffeine, alcohol and high-sugar drinks)
Staying in an air-conditioned environment
Limiting outdoor activities to the cooler early morning or early evening hours
Resting often in shaded areas and wearing plenty of sunblock (SPF 15 or higher) on the sun-exposed areas of the body
Replenishing the sunblock every two hours
Choosing lightweight, light-colored and loose-fitting clothing, a wide-brimmed, light-colored hat, and sunglasses
According to the CDC, people with heart disease and elderly people should be checked on at least twice a day during a heat wave and observed closely for signs of heat stroke or heat exhaustion. Children should be checked more frequently. People who suspect a heat-related illness in themselves or a loved one should contact a physician immediately. A quick reference chart at the end of this article can help individuals to quickly recognize the difference between heat stroke and heat exhaustion and administer first aid accordingly.
About heat-related illness
Heat-related illnesses occur when the body is unable to cool itself. Similar to the way that extreme cold can lead to hypothermia, exposure to high temperatures over a prolonged period of time can lead to hyperthermia, a potentially fatal condition in which a person’s body temperature rises above normal.
According to the U.S. Centers for Disease Control and Prevention (CDC), heat-related illnesses claim approximately 300 lives per year, which is normally more than most natural disasters in the United States. Though this number seems low compared to other conditions such as coronary heart disease (responsible for approximately 460,000 deaths annually), it is significant because heat-related illnesses are much more preventable.
The body normally cools itself by sweating. When air temperatures and humidity are high, the body’s sweat does not evaporate as quickly, preventing the body from releasing heat fast enough to cool the body. As a result, the body overheats, creating a rise in body temperature that can cause damage to the brain and other organs. Untreated, this temperature overload can result in death.
There are several types of heat illness, including heat stroke, heat exhaustion, heat cramps, heat rash and sunburn. Of these, heat stroke and heat exhaustion are the most common (with the exception of sunburn) and the most dangerous. Heat stroke can be fatal, and heat exhaustion can lead to heat stroke if it goes untreated. Signs and symptoms of these two conditions are quite different and learning to recognize them can save lives. A quick reference chart at the end of this article can help individuals to quickly recognize the difference between heat stroke and heat exhaustion and administer first aid accordingly.
Risk factors and causes of heat related illnesses
Certain factors increase a person’s risk of developing a heat-related illness. They include:
Environment. Hot weather, especially heat waves in areas that do not regularly experience them, is a major contributor to all heat-related illnesses.
Age. The elderly and young children (up to age 4) are at higher risk.
Heart conditions (e.g., coronary artery disease, high blood pressure)
Weight. Overweight and obese people are at higher risk. While the reasons for this are not entirely understood, it is partly due to the fact that body fat insulates heat within the body.
Mental illness. People with mental illness may be less likely to take basic precautions, such as avoiding prolonged periods in direct heat and drinking plenty of fluids. Some mental illnesses can even prevent individuals from realizing they are hot or thirsty. In addition, medications used to treat mental illness can increase the person’s sensitivity to sun or heat.
Medications that increase a person’s sensitivity to the sun or heat. These include:
ACE inhibitors. Medications that widen blood vessels and lower blood pressure.
Diuretics. Medications that cause the kidneys to flush water and other substances (e.g., sodium) from the body through urine.
Psychotropics. Medications used to treat mental disorders.
Parkinson’s disease medications. These substances can inhibit perspiration and therefore increase the risk of developing a heat-related illness.
Tranquilizers. Medications that reduce mental tension and anxiety without affecting normal mental activity.
Other factors also affect risk, including existing fever or sunburn, dehydration or alcohol use, and some illegal drugs, such as cocaine. The Centers for Disease Control and Prevention (CDC) recommends that people with heart disease and elderly people should be checked on at least twice a day during a heat wave and observed closely for signs of heat stroke or heat exhaustion.
About heat stroke
Heat stroke (or sunstroke) occurs when the body temperature rises. During episodes of heat stroke, body temperatures may rise to as high as 106 degrees F (41 degrees C) in only 10 to 15 minutes. Heat stroke can be fatal or result in permanent disability if not treated immediately.
There are two kinds of heat stroke. The first is slow-onset heat stroke in a fluid depleted person. This form of heat stroke may evolve from heat exhaustion as a person loses too much fluid through their sweat. Eventually, as fluid reserves are depleted, the body’s ability to cool itself through sweating breaks down, and core body temperature rises.
The second form of heat stroke is rapid-onset heat stroke in a person with adequate levels of fluid. This form of heat stroke occurs when a person is under extreme heat conditions. An example might be a bike rider climbing a mountainside road on a hot day in full sunlight. Even though the rider has fluid available, the heat challenge simply overwhelms the body’s ability to lose heat and the core temperature rises rapidly.
In either case, it is important to recognize the signs and symptoms of heat stroke. A quick reference chart is provided at the end of this article to help individuals quickly recognize the difference between heat stroke and heat exhaustion and administer first aid accordingly.
Signs and symptoms of heat stroke include:
Body temperature above 103 degrees F (39.4 degrees C)
Increased blood pressure
Red, warm (flushed) skin, which may be either dry (rapid onset heat stroke) or wet (slow onset heat stroke)
A strong, rapid pulse (tachycardia)
Throbbing headaches
Dizziness or fainting (syncope)
Nausea and/or vomiting
Disorientation or confusion
Seizures
Unconsciousness
Heat stroke is potentially fatal. Therefore, anyone exhibiting signs and symptoms should seek emergency medical care immediately. Next, the victim should be moved out of the direct sun and heat. If it is not possible to move into an air-conditioned environment, the victim should at least be moved into the shade. After calling emergency services, the first priority is to cool the victim’s body by any means possible. Keeping the victim’s head elevated, consider one of the following body-cooling techniques:
Place the victim in a cold shower or bath. Do not leave the victim unattended because loss of consciousness, muscle spasm or seizure may occur, creating a drowning hazard.
Place cold water or ice packs on the victim’s skin. Remove as much clothing as possible so that the cool water or ice is in direct contact with the victim’s skin.
Spray the victim with cool water from a garden hose. Make sure that the water is cool before spraying. Water that collects within the hose between uses may become warm on a hot day and would worsen the victim’s condition.
If the humidity is low, wrap a cool wet sheet around the victim and fan continuously. This will not work in high-humidity climates and may worsen the victim’s condition.
If the victim is vomiting, turn the person on his or her side to make sure the airway remains open. DO NOT give the victim any fluids to drink if he or she is vomiting, having muscle spasms or is experiencing seizures. The victim may aspirate the fluid (inhale it into the lungs rather than swallowing), which would lead to further injury. Victims who are not experiencing any muscle spasms, vomiting or seizures may be given some fluid to drink. Water is best, but if that is not available, avoid anything with alcohol or caffeine because these beverages may worsen the victim’s condition. The beverage should be cool but not too cold because drinking a very cold beverage may cause stomach cramps.
If a seizure occurs, shelter the victim from objects or other factors that might lead to injury. DO NOT place anything in the victim’s mouth during a seizure. If emergency medical personnel are delayed in arriving, call a hospital for further instructions. DO NOT give the victim any drugs, unless directed to do so by a physician or emergency medical professional.
About heat exhaustion
Heat exhaustion is less serious than heat stroke but can lead to heat stroke if left untreated. It often occurs after several days of repeated exposure to high temperatures coupled with not drinking enough fluids to replace what the body has lost through sweat.
Elderly people and those with high blood pressure are at particular risk for heat exhaustion, as well as those exercising in a hot environment. Signs and symptoms of heat exhaustion include:
Heavy sweating
Paleness
Skin may be cool and moist
A weak, rapid pulse
Shallow and fast breathing
Muscle cramps
Tiredness or weakness
Dizziness or fainting (syncope)
Nausea and/or vomiting
Heat exhaustion is not usually an emergency situation. However, if symptoms are severe, or if the victim has a history of high blood pressure or heart disease, a physician or emergency medical services should be called immediately. For others, the following steps should alleviate symptoms:
Get out of the sun. The victim should move to an air-conditioned environment. If the victim’s home is not air-conditioned, he or she should stay with a friend or call the local health department to locate a heat shelter. Such shelters are often set up during heat waves.
Cool off with a cold shower or bath. While not as critical in the treatment of heat exhaustion as with heat stroke, quick-cooling techniques can provide faster symptom relief.
Rest. Exertion will worsen symptoms. Victims should remain as inactive as possible until symptoms improve.
Drink plenty of fluids, preferably cool water or sports drinks. To avoid stomach cramps, take small sips and avoid beverages that are very cold. Also, avoid caffeine, alcohol or sugary drinks because they will cause the body to lose more fluids (dehydrate).
Heat exhaustion occurs, in part, because the body has been depleted of water (dehydrated) and/or salt. Therefore, victims of heat exhaustion who are taking diuretics (medications that reduce fluid levels in the body) or salt pills should contact their physician regarding the safety of taking their next medication dose.
If symptoms worsen or persist for more than one hour, contact a physician or emergency medical services. Because heat exhaustion can lead to heat stroke, it is vital to recognize heat exhaustion symptoms and follow basic heat safety tips. A quick reference chart is provided at the end of this article to help individuals quickly recognize the difference between heat stroke and heat exhaustion and administer first aid accordingly.
About heat cramps
Heat cramps are muscle cramps that are caused by a depletion of salt in the body. Along with moisture, the body loses salt in its sweat. When salt levels become too low within the muscles, they can begin to cramp. Heat cramps most often occur in people who are engaging in strenuous activity or exercise in high temperatures. However, they may also develop in people who are not used to the heat, sweat a lot or who do not drink enough fluids.
Along with muscle cramps (usually in the legs, arms or abdomen) the victim may also experience fainting or dizziness, weakness, and/or profuse sweating. Heat cramps can also be a sign of heat exhaustion and should be taken as a serious indication that the individual is overheated. People with heart conditions or who are on a low-sodium diet (such as those with heart failure or high blood pressure) should contact their physician if they are experiencing heat cramps.
If medical attention is not immediately necessary, a person experiencing heat cramps should take the following steps:
Stop all activity.
Find a cool, shaded place, preferably in an air-conditioned environment.
Drink clear juice or a sports beverage to replenish salt in the body (avoid caffeine and alcohol). Take small sips and choose a beverage that is cool but not too cold to avoid stomach cramps.
Avoid strenuous activity for several hours after the cramping stops. Failing to do so could lead to heat exhaustion or heat stroke.
Contact a physician if symptoms worsen or persist for more than one hour.
About heat rash and sunburn
While heat rash and sunburn are less serious heat-related conditions, they are still a clear indication that the individual has “overdone” it.
Heat rash, or prickly heat, is a skin irritation caused by profuse sweating in a hot or humid climate. It is most common in young children, but can occur at any age. While it can occur anywhere on the body, heat rash is most common on the chest, neck, groin, under the breasts or in elbow creases – areas where sweat is likely to pool or remain on the skin. It looks like a grouping of small pimples or blisters.
As with all heat-related illnesses, the best treatment is to move to a cool, dry environment, preferably with air-conditioning. While applying powder may ease symptoms, people should avoid using creams, lotions or ointments on areas of heat rash. These keep the skin moist and may worsen the condition. Most people will not need to seek medical advice for heat rash. However, a physician should be contacted if the rash is accompanied by other symptoms of heat–related illnesses (e.g., heavy sweating or no sweating, confusion, nausea and/or vomiting, paleness, muscle cramps).
Sunburns are well known conditions in which the skin becomes red, painful and warm after a period of sun exposure (or overexposure), due to exposure to harmful ultraviolet (UV) rays in the sunlight. Most sunburns are minor and heal in about a week. However, medical attention should be sought if the victim is under one year of age and the sunburn is accompanied by a fever, severe pain and/or fluid-filled blisters.
Cold compresses or cool water on the affected skin should ease pain, and moisturizing lotion may be applied. However, avoid using salve, butter or ointments because they may trap the heat and cause the burn to further damage skin. If blisters are present, the victim should not break them because this could lead to an infection.
Understanding heat index
The heat index is a measurement of perceived heat based on actual temperature and humidity. Similar to the way that wind can make a cold day feel even colder (wind chill factor), humidity can make hot temperatures seem even hotter. The heat index and wind chill factor provide measures of heat and cold that better reflect the danger posed by prolonged exposure.
Much as high humidity levels can make the temperature feel hotter, lower levels can make the temperature feel cooler. A temperature of 90 degrees F (32 degrees C) will feel like only 83 degrees F (28 degrees C) with 0 percent humidity, but it will feel like 100 degrees F (37.8 degrees C) if the humidity is 60 percent. The following table shows examples of how humidity and air temperature combine into a heat index number that better reflects perceived heat:
Air Temperature (Degrees F)
80
84
88
92
96
100
104
108
Relative Humidity
Heat Index
40%
80
83
88
94
101
109
119
130
45%
80
84
89
96
104
114
124
137
50%
81
85
91
99
108
118
131
55%
81
86
93
101
112
124
137
60%
82
88
95
105
116
129
65%
82
89
98
108
121
136
70%
83
90
100
112
126
75%
84
92
103
116
132
80%
84
94
106
121
90%
86
98
113
131
100%
87
103
121
Source: U.S. National Weather Service
(http://www.nws.noaa.gov/om/heat/index.shtml)
The following chart indicates the level of danger associated with heat index ranges, according to the National Weather Service:
A Heat Index of ...
Indicates...
80 to 90 degrees
Caution should be exercised.
90 to 103 degrees
Extreme caution should be exercised.
104 to 124 degrees
There is danger of suffering heat stroke in prolonged exposure.
125 degrees and higher
Extreme danger of heat stroke.
Source: U.S. National Weather Service
(http://www.nws.noaa.gov/om/heat/index.shtml)
It is important to note that it is possible to develop a heat-related illness even if the heat index is below 80. Individuals should always exercise basic precautions when spending time outdoors. However, a higher heat index serves as a warning to limit activity and heat exposure as much as possible.
Though the heat index, available shade, type of clothing and other factors all relate to the exposure risk, the most important factor is time. The longer the amount of time spent in the heat, the higher the risk for heat-related illnesses.
Prevention methods for heat related illness
The U.S. Centers for Disease Control and Prevention (CDC) offer the following tips for avoiding heat-related illnesses:
Drink plenty of fluids (avoiding caffeine, sugary drinks and alcohol) regardless of exercise or activity level. Sports drinks, which replace salt and minerals lost to sweating, are also recommended. People who wait until they are thirsty to drink are waiting too long and are at risk of a heat-related illness in hot or humid climates. Those people whose physicians have limited the amount of liquid they drink (e.g., for certain kidney failure and heart failure conditions) should ask for directions about how much they should drink when the weather is hot. They should also ask before drinking sports drinks since they may be high in sodium.
Avoid caffeine, alcohol and drinks with high amounts of sugar. These can actually cause the body to lose more fluid. Also, very cold drinks may cause stomach cramps.
Stay in an air-conditioned environment. Those whose homes do not have air-conditioning should go to a mall, senior center, public library, movie theater or other public, air-conditioned space. Even a few hours in air conditioning can help the body stay cooler when people return to the heat. During heat waves, agencies often set up air-conditioned heat shelters and people can call their local health departments for locations.
Plan outdoor activities. Those who must be outdoors in the heat should limit their activities to early morning or early evening hours when the heat and sun are less intense. Rest often in shaded areas, choose lightweight clothes that breathe and drink plenty of fluids. Also, wear plenty of sunblock (SPF 15 or higher) on any areas of skin exposed to the sun. The most effective sunblocks are those that say "broad spectrum" or UVA/UVB protection" on the labels.
Don’t rely on electric fans. While they may make people more comfortable, electric fans are not enough to ward off heat-related illnesses when temperatures reach the high 90s or humidity is high. Taking a cold shower or bath may help, but going to an air-conditioned environment is preferable.
Never stay in a parked vehicle (closed or open) or leave anyone within one, even for a moment. On a 90-degree F (32-degree C) day, temperatures within a parked car can reach 118 degrees F (47.7 degrees C) or higher. Each year, many children and pets die from being left in parked vehicles.
The CDC recommends that people with heart disease or elderly people be checked on at least twice a day during a heat wave and observed closely for signs of heat stroke or heat exhaustion. Children should be checked frequently. People who suspect a heat-related illness in themselves or a loved one and are uncertain of the severity of illness should call emergency medical services, or if illness is mild, contact a physician immediately).
Working outdoors and heat related illness
Some people are required to work outside, even in extreme heat. These include construction workers, landscapers, athletes and others. While they are at far greater risk for heat–related illnesses, there are steps these individuals can take to ensure their health, even in extreme heat conditions.
These precautions include:
Rest often in shaded areas. Those wearing hats or helmets should take them off when resting and apply cool water or ice to the back of their necks. A major portion of the body’s heat escapes through the head and neck. Therefore, while hats can help to keep people cooler when they are in the sun, removing them while resting in the shade can help to cool the body down.
Drink two to four glasses of fluid each hour (no alcohol, caffeine or high-sugar drinks). People can literally lose pounds of water when working in the heat and humidity, especially if they are overweight. Heat exhaustion develops because that water is not replaced over time. For instance, an individual may lose 10 lbs. (4.5 kg) of water weight during one day of working or vigorously exercising during a heat wave, but only replenish 8 of those pounds (3.6 of those kilograms) by drinking. The next day, the individual is already beginning with a 2-lb (1 kg) deficit of water in the body. After a few days, the individual has lost 6 lbs (2.7 kg) of water and is on the way to developing heat stroke.
Wear plenty of sunblock (SPF 15 or higher) on any areas of skin exposed to the sun and reapplying it every two hours. Sunburns generate heat, adding to the burden of an already overheated body.
Wear lightweight, light-colored and loose-fitting clothing. The best clothing for the heat is made out of cotton or any other material that “breathes” (allows air to flow through it). Also, wearing a wide brimmed, light-colored hat and sunglasses are recommended.
Use the buddy system. Overexposure to heat can cloud a person’s judgment, leading to a heat–related illness and other occupational injuries. People working together can keep an eye on each other for signs of overexposure (e.g., confusion, nausea and/or vomiting, heavy sweating, paleness, muscle cramps) as well as encourage each other to take preventive measures.
Eat small, frequent meals. Large meals are more difficult to digest and the body generates additional internal heat. In addition, high-protein foods such as meat and nuts will increase metabolic heat. Avoiding these foods when working in hot temperatures can help in avoiding a heat-related illness.
Get training. Taking a safety course can help individuals better recognize the signs and symptoms of heat-related illness. Such courses are offered by organizations such as the American Red Cross.
Heat stroke vs. heat exhaustion
It is important to understand the difference between heat stroke and heat exhaustion. Not only are the symptoms different, but the first aid recommended is also different. In fact, giving first aid for heat exhaustion to a person with heat stroke could actually worsen their condition. The following quick reference table is provided to help differentiate between these two conditions.
HEAT STROKE
HEAT EXHAUSTION
Primary symptoms:
Hot skin that is either dry (rapid onset) or wet (slow onset)
A strong, rapid pulse
Body temperature above 103 degrees F (39.4 degrees C)
Heavy sweating
Pale, cool and clammy skin
A weak, rapid pulse
Body temperature may be high or normal
Other symptoms:
Nausea and/or vomiting
Dizziness or fainting (syncope)
Disorientation or confusion
Throbbing headaches
Unconsciousness
Nausea and/or vomiting
Dizziness or fainting (syncope)
Muscle cramps
Tiredness or weakness
Shallow and fast breathing
Is this an emergency?
Yes. Call emergency services (911).
Call 911 if:
Symptoms are severe
The victim has a history of high blood pressure or heart disease
You are uncertain of the severity of illness
For others, if symptoms worsen or persist for more than one hour, contact a physician or call 911.
What to do next:
Get out of the sun. If the victim cannot be moved quickly to an air-conditioned environment, at least find a shaded area to wait for emergency medical personnel.
Cool the person’s body by any means possible:
A cold shower or bath
Ice packs placed on the skin
Spray with cool water from a garden hose
Wrap a cool wet sheet around the victim and fan continuously (only if humidity is low)
If vomiting, turn the victim on his or her side to make sure the airway remains open.
Stay with the victim to make sure that loss of consciousness, seizures or muscle spasms do not lead to further injury.
If emergency medical personnel are delayed in arriving, call the hospital for further instructions.
Get out of the sun. The victim should move to an air-conditioned environment. If the victim’s home is not air-conditioned, he or she should stay with a friend or call the local health department to locate a heat shelter.
Cool off with a cold shower or bath. While not as critical in the treatment of heat exhaustion as with heat stroke, quick-cooling techniques can provide faster symptom relief and help prevent deterioration into heat stroke.
Rest. Exertion will worsen symptoms. Victims should remain as inactive as possible until symptoms improve.
Drink fluids, preferably cool water or sports drinks (not too cold or it may cause stomach cramps). Avoid caffeine, alcohol or high sugar drinks. Take small sips.
Change into lightweight clothing, preferably cotton or other material that breathes.
What not to do:
DO NOT give any alcohol or caffeine to the victim or any fluid at all if the victim is having muscle spasms or seizures.
DO NOT give any drugs to the victim, unless directed to do so by a physician or emergency medical personnel.
DO NOT place anything in the victim’s mouth if he or she is having muscle spasms or seizures.
DO NOT drink beverages with alcohol, caffeine or high sugar content because they will cause the body to lose more fluids (dehydrate)
Questions for your doctor
Preparing questions in advance may help patients have more meaningful discussions with their physicians about their conditions. Patients may wish to ask their doctors the following questions about heat-related illnesses:
How long can I work in the sun before developing heat exhaustion?
Are any symptoms of heat-related illness normal?
Will my medications make me more susceptible to heat illness symptoms?
If I get a sunburn, will I get symptoms of heat exhaustion or heat stroke?
If I keep drinking water, can I avoid heat exhaustion completely?
At what point does normal sweating in heat become a heat-related illness?
If I cannot seek immediate medical attention, will a physician be able to diagnose a heat-related illness later on?
If I had heat stroke once, am I more likely to get it again?
Is it possible to get heat exhaustion while resting?
I have a heart condition. How much hot weather is acceptable for me?
