What Really Is Fever?

Fever (Pyrexia) is abnormally high body temperature. Beyond that, there is much confusion amongst the public about what exactly is abnormal in terms of body temperature and what action should be taken.

Read on to learn the answers to your questions:
 - Why does temperature rise?
 - How do the different methods of measuring temperature compare?
 - What constitutes abnormal temperature?
 - If and when is it appropriate to use two anti-pyretic agents to reduce temperature?
 - What other action might be recommended to control temperature?
 - When should medical advice be sought?

Body temperature is controlled in part of the human brain. When the immune system senses an infection or other trigger, it releases substances called pyrogens. The pyrogens act indirectly on the brain causing it to raise the temperature of its thermostat. The body then reacts to conserve and produce heat, causing the temperature to rise. Blood vessels near the skin surface constrict and shivering begins, so as to prevent heat loss from the body.  
When the invading disease or trigger has been controlled by the body or antibiotics, the temperature setting in the brain will drop to the normal level. The body then needs to cool itself to return to the new setting in the brain. The skin becomes flushed and warm, and the person begins to sweat.

Fever triggers the release of substances from cells in the body and increases the heart rate. Both these actions boost the activity of the immune system and so fever can be beneficial in normal adults. A high body temperature may also help to prevent the growth of some types of bacteria. However, fever that is very rapid, high or prolonged and/or does not respond to treatment can result in dehydration (excess fluid loss from the body), excess acid build-up in the body and brain damage. Young children and the elderly are by far and wide much more susceptible to the ill effects of fever than normal adults. Hence the emphasis on keeping a watchful eye for signs of fever in babies.


  • Normal ORAL temperature is 37 degrees Celsius, but it is still normal if this varies up or down by 1 degree ( - Average 37.8).
  • Normal UNDERARM (axilla) temperature is 0.5 degrees lower than oral temperature ( - Average 37.3).
  • Normal RECTAL temperature is about 0.5 degrees higher than oral temperature ( - Average 38.2).
  • Normal EAR temperature can range from 38.5 degrees to 38 degrees, depending on the age of the child.

Children should not have their temperature measured routinely by the oral or rectal route and forehead strips are unreliable. In children younger than 4 weeks the recommended method is axilla measurement using an electronic thermometer. In children over 4 weeks but younger than 5 years of age, ear temperature may be as reliably used as axilla measurement.

Fever is very common in children and is usually associated with viral and bacterial infections. Parents should be alerted to the possibility of fever by the following symptoms:

  • Infants: irritability, fussiness, lethargy, quietness, heat or warmness, change in eating or sleeping habits, crying, rapid breathing.
  • Children who can Talk: headaches, body aches,difficulty sleeping or sleeping more, heat or coldness, change in appetite.

Other symptoms may be present depending on the cause of the fever.

Fever should be treated if the child appears distressed or unwell, and not with the sole aim of reducing body temperature.

Paracetamol and ibuprofen are effective antipyretics - that is, they bring the temperature down. Both are formulated as liquids for children, while tablet and capsule options are available for older children and adults. Paracetamol is also formulated in suppository form; this is a very effective alternative where vomiting is occurring.

Aspirin must be avoided in children younger than 16 years of age due to the possibility of Reye's Syndrome. In adults, however, it may be chosen as an anti-pyretic.

For most minor ailments accompanied by fever, paracetamol is a suitable first-line agent. Some parents prefer ibuprofen for certain types of fever-producing ailments, such as minor ear infections. No matter the first choice, however, it is advised against administering paracetamol and ibuprofen at the same time. Rather, one agent should be used up to the maximum dosage appropriate for the age. If an adequate response is not produced by this first drug, then it is appropriate to also use the alternative agent. The two anti-pyretics should be administered in a staggered fashion. Your pharmacist will assist you with devising this protocol.

Other Action:
 - Children should be given extra fluids when they are running a temperature. This will help protect them against dehydration. Where the fever is severe, and/or if it is accompanied by diarrhoea or vomiting, then it is appropriate to use a rehydration formula, such as Dioralyte or Rapolyte sachets available in the pharmacy.
Adults, too, should drink plenty of fresh, filtered water when running a temperature. Coffee, tea and cola drinks should be avoided as their caffeine content can promote dehydration.
 - Tepid sponging is no longer recommended. (This may cause shivering which will drive the body temperature up further.)
 - Children should be neither over- nor under-dressed.
 - Physical exertion and stress should be avoided during a fever. These factors may aggravate the symptoms and delay healing of the body.

If you are worried about your child, or if you have doubts about the reduction in temperature achieved, your pharmacist is there to advise you. There are some instances where it may be necessary to take your child to the doctor, for example:

  • Any unexplained fever in a child under 3 months.
  • Fever unaccompanied by other symptoms (may be indicative of urinary tract infection).
  • Febrile convulsions.
  • No response to anti-pyretic medication or any deterioration in condition.
  • Suspicion of an "ill child" (pallor, lethargy, rapid breathing, dehydration, prolonged fever, non-blanching rash, neck stiffness, etc.).

In the case of older children and adults, emergency assistance should be sought for those who exhibit signs of confusion or unconsciousness.
Medical assistance should also be sought for those who experience:

  • A temperature of or greater than 40 degrees Celsius.
  • Fever that lasts more than 7 days.
  • Worsening of symptoms.
  • Other accompanying symptoms, such as excessive sleepiness or confusion, stiff neck, severe headache, sore throat, rash, chest pain, repeated vomiting, pain with urination, leg swelling, a red or swollen area of skin.

People with serious medical illnesses, such as cancer or HIV, or those people on immuno-suppressants, may not show these warning signs and should seek medical assistance immediately if they develop a fever.