Dehydration is the loss of water and salts essential for body functions, which occurs when more liquids and salts are lost than taken in.
Many things can cause dehydration: feverish illness, medical treatment with diuretics, high external temperatures and inadequate water consumption.
Diarrhoea, vomiting, excessive loss of liquids through sweating or urination, and inadequate water consumption are also possible causes of dehydration.
The very young and very old most at risk
Those most at risk from dehydration are the very young (less than one year old) and the elderly, those with chronic disorders, anyone with a fever and people who live in hot and humid climates.
Dehydration caused by diarrhoea is a cause of infant death. Illnesses involving diarrhoea are cholera, typhoid fever, salmonella and E. Coli infection, amongst others. It is quite possible for a small child to become severely dehydrated within a matter of hours.
General weakness prevents children from compensating for excessive loss of water and in adults over 60 a low level of sensitivity to the thirst stimulus could lead to dehydration.
Risk higher in hot climates
The risk of dehydration is higher in hot, humid and excessively dry climates.
Symptoms of dehydration
The symptoms of slight dehydration are thirst, dry mouth, dark urine, difficulty in concentration and slight headache.
The symptoms of moderate dehydration are slightly more severe, though. These include flushing in the face, intensive thirst, dry, hot skin, small amounts of dark-coloured urine, dizziness which worsens when the person stands up, general weakness, cramps in the arms and legs, irritability or sleepiness, discomfort, headache, a dry and furry mouth, dry tongue, cracked lips and dense saliva.
Symptoms of moderate to severe dehydration are hypotension, muscle contractions in the arms, legs, stomach and back, lethargy or convulsions, uneven heartbeat, swollen stomach, sunken eyes, wrinkled skin, weak or racing pulse and quick, deep breathing.
The symptoms of severe dehydration may be anuria (no urination for six hours) and the inability to drink water. Severe dehydration requires hospitalisation and intravenous therapy. Medical treatment is needed immediately in order to avoid kidney failure.
A doctor must be called when:
- A baby is less than three months old and has a temperature of over 38 degrees Celsius;
- A baby is more than three months old and has a temperature of over 39 degrees Celsius;
- There is a reduction in the amount of urine that is passed;
- There is a worsening of the signs and symptoms of dehydration;
- The person appears apathetic, dizzy and has other neurological signs and symptoms;
- There is a loss of more than 1.3kg in one day or 2.3kg in one week in a person using diuretics.
- (World Health Organisation, updated February 2014)