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High temperature

Normal body temperature in humans is 37°C. This is the temperature that most enzymes in the human body work best at. Moving away from this temperature reduces the effectiveness of the human body and can ultimately lead to death.

Hyperthermia occurs when the human body temperature increases beyond 37.5 to 38.3°C. A slightly smaller increase in temperature is called a fever. The two main causes of hyperthermia are:

• heat stroke
• adverse reaction to drugs

Heat stroke occurs when the body cannot cool itself anymore. Sunstroke is a type of heat stroke caused by direct exposure to the sun for too long a period. They both can be fatal if not treated properly by a slow and steady decrease in temperature.

Symptoms of heat stroke include:

• tiredness and weakness
• lower blood pressure
• headaches and muscle cramps
• heavy sweating and intense thirst
• small volumes of darkly coloured urine

Low temperature

Hypothermia occurs when the human body loses more heat than it can generate and drops below 35°C. This can happen quickly if, for example, someone fell into cold water. This is called acute hypothermia. Exhaustion hypothermia happens when the body is so tired it cannot generate enough heat. This is a form of chronic, or longer term, hypothermia.

Babies, the elderly and homeless people are at particular risk of hypothermia. Symptoms include:

• shivering
• tiredness
• pale skin
• low energy

Hypothermia is treated by a slow and steady increase in temperature. Without this hypothermia is fatal.

Dehydration

Dehydration occurs when your body loses more fluid by sweating and urinating than it can take in. This often occurs in hot conditions when more sweating occurs. Symptoms of dehydration include:

• feeling thirsty and having a dry mouth
• tiredness
• small volumes of darkly coloured urine

Babies, the elderly and athletes competing in hot conditions are most likely to suffer dehydration.

Dehydration puts strain on your kidneys to retain more water. Your urine becomes more concentrated as more water is retained. People suffering from dehydration need to consume water and also salts that may have been lost during sweating, vomiting and diarrhoea. Rehydration sachets are used to do this.

Excess water intake

Consuming too much water can be as dangerous as not having enough under certain conditions. It is much rarer than insufficient water, but consuming excessive volumes can also lead to death.

The kidneys balance the levels of water and salts in your body. Consuming too much water causes cells in the body to swell. This happens in the brain which increases pressure on the skull. This leads to:

• headaches
• personality and behavioural changes
• irritation and drowsiness
• nausea and vomiting

Without treatment this can lead to seizure, brain damage, going into a coma or death.

High salt intake

Increased salt levels in the body can occur when a person consumes too much salt or loses too much water by sweating, vomiting and diarrhoea. Both result in too much salt and not enough water. Symptoms of too much salt include:

• thirst
• confusion
• muscle twitching
• bleeding in the brain causing damage

The kidneys balance the levels of water and salts in your body. Consuming too much salt or not enough water puts pressure on the kidneys. This can lead to kidney damage and failure, which in turn can be fatal.

Babies and the elderly are most likely to suffer from problems relating to high salt levels.