What Causes Fever?
Fever is the body’s sign that it is fighting infection and helps mobilise the immune system. A fever will also hinder the function of bacteria and viruses. In most children the fever is caused by a virus, but more serious bacterial infections need to be considered. When doctors see a child with a fever there are a number of ‘rules’ that if followed will avoid missing a serious cause. The most important part is getting an overall opinion of how unwell the child is. Age, colour, hydration, level of activity, breathing rate, pulse rate, state of alertness are all factors that should be assessed. An unwell infant, who appears lethargic and has a temperature of 38 degrees is far more concerning than a well looking healthy child with a high temperature approaching 40 degrees.
Measuring a fever
Fever is measured by either a digital under the arm thermometer, or an infrared ear or forehead device. A fever is generally any temperature above 37.4 degrees celsius. A low reading around 35 to 36 is usually due to poor contact with the skin. This is not a concern.
Fever in an infant.
- An infant under 3 months with a fever needs to be assessed urgently. If the cause of the fever is unclear on history and examination then investigations such as urine and blood examination are required. This is because this age is vulnerable to serious infection. Immune protection is poor and barriers to infection are not mature. Infants can deteriorate quickly and are ‘hard to read’. This should be done in a hospital with good paediatric support
- An infant between 3 – 12 months with a temperature can be reviewed by a GP depending on how unwell he or she is. The most common causes are viruses, such as coughs, and colds. Tests will be unnecessary unless the infant appears unwell. However if there is no obvious cause for the fever, further investigations are needed. The most common cause of fever that is not due to a virus is a urine infection, particularly in infant girls. If the infant is unwell then hospital assessment is mandatory.
Fever in toddlers – 12 to 36 months
- Between 12 – 36 months of age fully immuniseed toddlers with a fever will generally be due to viruses. However if after examination and history the cause of the fever is still unclear and the child appears unwell then further investigations are needed, such as urine and blood tests.
Fever in children
- Older children will have a more mature immune system and in most instances the cause of the fever is obvious and can be managed accordingly.
- If a fever lasts more than a few days it is worth being assessed, especially if the source is unclear.
- Dress your child in light clothing
- Give your child frequent small drinks of clear fluid (eg. water, diluted fruit juice or cordial). Do not worry if your child refuses to eat at this time. If your child is under six months give extra cooled boiled water, breast feeds, or bottle.
- Paracetamol or nurofen can be given especially at night when the child fever can cause irritability and discomfort.
- Cool flannel to forehead will help with the discomfort but is not essential
Febrile Convulsions and other Fever Facts
- A fever generally means 38 degrees or above. Viruses and bacteria do not like a higher temperature.
- Cool baths to ‘get the fever down’ are not recommended and are not necessary.
- If the child is otherwise well, and the source of the fever is known, (such as a cold or sore throat) then the height of the fever is of little consequence
- Febrile convulsions occur in only 3% of the population. There is no evidence that controlling a fever with panadol, or sponging etc will prevent those that are susceptible from having a seizure. Many in the health profession will be unaware of this and will contribute to a parent’s concerns about fever by concentrating on trying to lower the temperature.
- There is no such thing as brain damage from a fever caused by an illness. Prior to the 19th century this was a common held theory and people died during febrile illnesses. In those days microbiology and science was only just starting to understand how infections worked. It was discovered the fever was a side effect of the infection not the cause of death or brain damage.