Man flu? It’s a fact.

A new study shows that estrogen actually fights the flu.

Man sick in bed blowing his nose.  Marc Romanelli/Getty Images

Marc Romanelli/Getty Images

The latest battle of the sexes has gone viral. No, really: researchers at Johns Hopkins University have found that when it comes to who gets sick with the flu virus less often, women win because of estrogen’s protective quality.

The study shows that estrogen, the primary female sex hormone, reduced the replication of the influenza A virus in the nasal cells of women but not men. Replication is how the flu makes people sick. Estrogen also seemed to initiate antiviral effects against the flu—which lines up with previous studies showing the hormone has properties to fight HIV, Ebola and hepatitis.

The researchers say these findings suggest “therapeutic estrogen” used to treat infertility or menopause may, potentially, help stave off the flu, too.

The study, published this week in the American Journal of Physiology—Lung Cellular and Molecular Physiology, seems to further confirm another long-debated issue among men and women: whether the “man cold” is a real threat.

In 2013, a study by researchers at Stanford University showed high levels of testosterone, the primary male sex hormone, weakens a man’s immune response to the flu shot compared to women who are vaccinated against the virus.

Whether men suffer more sickness more intensely than women was parodied in a BBC video that’s been watched more than 4.7 million times on YouTube. The gist: a wife is confused as to why her husband has called the paramedics after he catches her cold; the paramedics (male themselves) are indignant: “For God’s sake, woman, he’s a man—he’s got a man cold.”

The medic may actually have raised an important point: it would seem that men are, in fact, the more vulnerable sex when it comes to the cold and flu.

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