Just because a guy cowers in bed with aches and chills, while his girlfriend barely catches the sniffles, doesn't make him a wuss.
Women are simply less likely to succumb to bugs, the Telegraph reports.
Compared with men, an Australian study found, women have a "much stronger immune response" to rhinoviruses – the germs responsible for the common cold.
In other words, "man flu" is real. And contrary to what their reluctant nursemaids mutter under their breath, male sufferers aren't being melodramatic.
Derogatory comments about man flu are so pervasive that a gag cold remedy has a label saying "Contains no artificial comfort or sympathy." Meanwhile, the satiric website Manflu.info insists "the only way to combat the crippling effects of Man Flu is complete withdrawal to the sofa and uninterrupted mollycoddling by the girlfriend/wife."
But women shouldn't be too quick to gloat.
A woman's bug resistance fades after menopause, notes John Upham, co-author of the study and professor of respiratory medicine at the University of Queensland. "Hormones obviously play a huge part in helping fight viruses," he told the Telegraph.
The report confirms earlier research at McGill University, which found the sex hormone estrogen boosts women's immunity by blocking the expression of a gene that leaves the body vulnerable to infections.
McGill researchers suggested an immune-boosting treatment containing estrogen may be available somewhere down the road.
Hopefully, guys will be man enough to take it.
Do you still think men should "man up" when they come down with "man flu?"