Taking paracetamol doesn't make adult flu sufferers feel better or significantly reduce fevers, but won't prolong the illness, a study has found.

Taking paracetamol doesn't make adults feel better when they have the flu, a New Zealand study has found.

But at least it won't make them sick for longer.

Scientists looked at the severity and duration of flu symptoms in 80 people taking either paracetamol or a placebo.

They found that there was no difference between the paracetamol and placebo groups in terms of severity, duration, temperature, or viral-load, which indicates paracetamol had no beneficial effect.

Paracetamol is currently recommended for reducing flu fevers and researchers were concerned this would prolong the illness as the influenza virus cannot replicate as well at higher temperatures.

"Fortunately this was found not be the case," Dr Irene Braithwaite, a senior investigator said.

"Paracetamol was neither harmful nor beneficial. We found that it did not significantly reduce temperatures compared to a placebo and did not make the participants feel any better."

However, Dr Braithwaite said a recommendation for or against the use of paracetamol by adults with flu-symptoms could not be made based on these results.

"Given the findings it is even more important that those at risk, particularly pregnant women, the very young, the old, and those with chronic medical conditions should have the annual influenza vaccination."

The study published in Respirology on Monday is believed to be the first of its kind.

It was a collaboration between the Medical Research Institute of New Zealand, Otago University Wellington, Capital and Coast District Health Board and Canterbury Health Laboratories.