You’re achy and lethargic. Your muscles shake. You get chills one minute and are on fire the next.
Having a fever feels horrible and chances are you will try to bring your temperature down – either with medicine, like paracetamol, or other measures, such as tepid baths, stripping off clothing and blankets, lying under a fan and so on.
But do you actually need to treat a fever?
Probably not in most cases, says Dr Paul Young, an intensive care specialist at Wellington Hospital in New Zealand and fever researcher. In fact, it might be important to leave a fever alone.
While quality research has been lacking, there’s some evidence that shows reducing a fever actually hinders recovery from infections, the cause of most fevers in the community, Young says.
But whether slowing down your recovery is an issue might depend on how sick you are.
For mild illnesses like colds, “if it takes you one day longer to get better but you felt better throughout the illness then it might be worth it,” Young says.
Also, if you take paracetamol to lower a fever, it may make you feel better because it also acts as a painkiller. (Whether lowering a fever in itself makes you feel better isn’t clear.)
But when you’re critically ill, some evidence suggests treating a fever might make it less likely you’ll survive.
“At the moment, we use paracetamol all the time. It’s given to more than half of patients in intensive care units on any given day and yet, we don’t know if the fact it reduces temperature is a bad thing.
“We don’t know where the balance of risks and benefit lies at the moment.”
The frightening idea that treating a fever might sometimes kill people stems from a study in which Young was involved, published in the journal Intensive Care Medicine earlier this year.
It looked at over 600,000 intensive care patients and showed that in those with infections, the higher the fever in the first 24 hours after admission, the lower the death rate.
“There’s a cost that comes with having a fever,” says Young. “You tend to have a higher heart rate, you tend to breathe faster and the metabolic demands on your body are generally increased. In the absence of infection this might be a bad thing. But if you have an infection, the fever seems to help kill the bugs.”
Whether leaving a fever alone could make the difference between life and death is being tested in a follow-up study. The results should be available in 2015.