Body of evidence
The idea fever is helpful in fighting infections isn’t new, however. Before antibiotics were invented in the late 19the century, therapies based on fever were widely used.
Demonstration of the fact that fever from malaria could cure paralysis caused by the sexually transmitted infection, syphilis, was the basis of a Nobel Prize in 1927.
“We’ve come full circle,” Young says. He is not sure why it is now more routine to treat fevers, but says it doesn’t seem to be based on evidence and may relate to the development and marketing of drugs.
More recently, it’s been shown treating fever:
- increases death rates from infections in animals
- worsens nasal symptoms in children with colds
- prolongs blisters in children with chickenpox
- blunts the immune response triggered in children in response to vaccinations
“Basically everything that’s more evolved than a cartilaginous fish gets a fever when they get an infection. For it to have evolved and been preserved across all of biology without having a [useful] purpose would be very unusual.”
One reason we try to bring a fever down is fear the temperature will keep rising and cause damage to the brain and other organs.
It’s true that temperatures over 41 degrees Celsius can be harmful but such high fevers usually occur only with events like heat stroke, where our ability to regulate temperature is disrupted.
In contrast, fevers from infections happen because they trigger a resetting of the “thermostat” in our brains. In general, this probably causes our bodies to “mount a response aimed at raising our temperature only to a level that’s needed to kill the bugs,” Young says.
“After that, the fever will go away. I think there’s very little evidence [infections from fevers] will keep getting higher and higher or that the fever in and of itself will be harmful.”
However, high fevers from infections can cause fits or seizures (also known as febrile convulsions) in about one in 30 children. (Check out our Fact File: Fever for more.)
But Young says there isn’t evidence that treating fevers reduces the risk of febrile convulsions. Attempting to bring a fever down rapidly, say in a cold both, can actually trigger a seizure, says Clinical Professor Dominic Fitzgerald, a paediatric respiratory specialist at The Children’s Hospital, Westmead in Sydney, Australia.
Says Young: “if you’ve got an infection, my gut feeling is that it’s not important to treat the temperature but I don’t think we have proof of that yet. What I can say is that using paracetamol and other drugs to treat temperature in the way they’re used commonly is not based on anything other than experience.
“There’s no reason to suspect leaving the temperature to go up would be bad in terms of your ability to fight infection and there’s a lot of data to suggest it’s probably often a good idea.”