By Danielle Braff

“Man flu” has become a silly term to describe how men seem to have a lower tolerance than women do for being sick, but there may be some truth to it, according to a recent study published in the journal Brain, Behavior and Immunity.

In that study, adult male mice had more symptoms of illness than females did when they were given the same bacteria, causing symptoms similar to the flu.

The male mice also had more fever fluctuations and inflammation, and they even took longer to recover than the female mice did.

Another study, published in 2010 from the University of Cambridge, found that men evolved to have weaker immune systems because they tend to have greater risk-taking behaviors.

This theory was tested in a study published in the American Journal of Physiology, where the influenza A virus was used. Researchers looked at how the virus affected men and women differently, and they infected nasal cells (these are primarily targeted by the virus) from men and women. They found that estrogen has a greater resistance to infection because of its antiviral qualities, possibly because of its ability to reduce the virus from replicating.

A more recent study from Royal Holloway University of London, published in 2016, in Nature Communications, suggested that any type of virus — in a show of self-preservation — may go easier on women because they can spread pathogens to their children during pregnancy, birth and breastfeeding.