Dehydration and hot weather
The human body contains a high proportion of water, so when the temperature rises and the body tries to cool itself by sweating, dehydration can be a real concern, particularly for children.
What is dehydration?
Dehydration is the loss of water and salts from the body. We need water to maintain enough blood and other fluids to function properly, and to maintain our blood pressure. Along with the fluids, the body also needs electrolytes, which are salts normally found in blood, other fluids, and cells.
How do we lose fluid?
The body may lose fluids in a variety of ways:
- when urinating;
- when you vomit or have diarrhoea;
- when sweating; and
- from the lungs when you breathe.
Why do we need water?
The human body consists of nearly 60 per cent water; brain tissue is said to consist of about 85 per cent water. This is why drinking 6–8 glasses of water a day helps our body function efficiently. It is estimated that if we lost just one-tenth of the water within our body, we would not be able to stand, let alone walk.
Although fluid loss occurs during hard physical work, even simple tasks like gardening, walking or riding a bike can result in a significant loss of fluid within a very short period. We can also lose a lot of fluid in hot or humid conditions.
Babies and small children feel the effects of heat sooner and more seriously than adults. Children in cars need special protection from heat as cars can heat up very quickly. A parked, locked car can reach dangerously high temperatures very quickly, even if the windows are open slightly. You should never leave a child in a parked car — your child can quickly become overheated and dehydrated, with potentially fatal consequences.
At highest risk of dehydration are babies under one year old, particularly if they are suffering from diarrhoea or vomiting.
Stages of dehydration
The early stages of dehydration usually have no signs or symptoms, but can include dryness of the mouth and thirst. Other symptoms in early or mild dehydration may include dry, warm skin; dizziness; or cramping in the arms and legs. As dehydration increases, signs may include:
- a flushed face;
- rapid pulse;
- dark, yellow urine;
- passing less urine than normal;
- sunken eyes;
- in infants, a sunken fontanelle (the soft spot on the top of the head);
- skin that has lost its elasticity and doesn’t quickly return to its normal position after being pinched;
- irritability or drowsiness;
- irrational behaviour; and
- absence of tears when crying.
If you are with someone, particularly a child or young person, who suddenly becomes dizzy, nauseated or weak during hot weather, get them indoors or in the shade. Replace lost fluids with cool water and cool the person down with a cool shower or sponge bath. Seek medical attention if the symptoms get worse or last for more than an hour.
If someone has dry, red skin, has a fast pulse, looks confused or delirious, or feels very hot, that person is in extreme danger and you should seek medical attention immediately, as well as taking the steps outlined above. In severe cases, dehydration can result in shock and even death.
How do I combat dehydration during hot weather?
Water should be given to counteract dehydration. It should be drunk before you get to the stage of feeling thirsty. It’s best to remember that other drinks, such as soft drinks, coffee, or alcohol-containing beverages, are no real substitute for water. Although they contain water, they may also contain dehydrating agents.
So-called isotonic sports drinks can replace some of the salts lost when sweating during intense or prolonged exercise, and are an appropriate fluid replacement in this setting.
If you are sweating profusely or have vomiting or diarrhoea, oral rehydration solutions such as Gastrolyte and Hydralyte are also suitable. They should be made up and given according to the manufacturer’s instructions.
Preventing dehydration during hot weather
It is recommended that during hot weather we should be drinking water even when not thirsty. Drink at least one-and-a-half cups of water every half hour and at least one-and-a-half cups of water 20–30 minutes before playing or exercising in the heat.
Other things you can do to avoid dehydration during hot weather include:
- avoiding the sun in the middle of the day — exercise or do outdoor activities early in the morning or evening instead;
- wearing sunscreen and a hat that shades your head, neck, ears and face — sunburn stops your body from cooling itself down properly;
- wearing thin, loose clothing — this allows good airflow, which helps sweat evaporate; and
- avoiding dark clothing, as this absorbs more heat than light clothing.
By recognising the signs of dehydration and taking measures to prevent it, you can look forward to a sizzling, and safe, summer.
Last Reviewed: 17 May 2007
