If you ask most women about how their male relatives, partners and friends respond to being sick, they’ll often tell you with an accompanying eye roll: “He’s such a baby,” “he’s extra whiny,” or “he exaggerates so much.”

But there may be a biological explanation for this behavior.

Dubbed the ‘man flu’, this phenomenon has been validated in a review of previously published, large epidemiological studies, as well as in studies of influenza in animals.

In these studies, males were sick longer, with more severe symptoms and had a weaker response to vaccination. Laboratory tests with animals infected with the influenza virus also underscore that there are sex-based differences in immune response that influence outcomes observed in humans.