Treating a fever could do more harm than good, say New Zealand researchers.

The researchers will carry out a study on 80 flu patients next winter to test their theory that it is better to let a fever run its course, as taking drugs could be risky.

The team from the Medical Research Institute and Capital and Coast District Health Board have looked at previous trials on animals in which common treatments such as aspirin, paracetamol and ibuprofen were used to treat fevers.

Their study has been published in the Journal of the Royal Society of Medicine.

Study co-author Kyle Perrin said the results were striking, and showed that animals given drugs to fight a fever were more likely to die from flu. "The ones treated with anti-fever agents died at about a 30 per cent higher rate. It was as simple as that."

The results led the team to believe fevers could be a natural protective mechanism which kicked in when animals had flu, to improve their chances of survival.

The study this winter would help them understand whether the same was true for humans.

"When you review everything it seems pretty clear to us that the presence of a fever response in all animals, including humans, is protective."

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