Fever without a source

What it is

Fever without an apparent source is a raised temperature where examination finds no origin. The cause is usually viral, but in a young child it calls for particular caution.

Red flags

Examine immediately — suspect a serious bacterial infection — if any one is present:

• age under 3 months with a temperature of 38 °C or higher;

• lethargy, the child is hard to wake, a weak or monotonous cry;

• a petechial or non-blanching rash;

• laboured or grunting breathing;

• cold extremities, mottled skin, capillary refill longer than 3 seconds;

• seizures, a bulging fontanelle, neck stiffness.

What to do

• assess the child's overall state, not just the number on the thermometer;

• plenty of fluids; an antipyretic (paracetamol or ibuprofen dosed by weight) for impaired wellbeing, not for the number itself;

• watch for a source appearing: rash, cough, painful urination.

What does not help

• antibiotics “just in case” with no source and no indication;

• alternating paracetamol and ibuprofen by the clock to push the number down;

• sponging with alcohol, cold wraps.

Related topics

If a seizure occurs during the fever — see Febrile seizures.