Women have long disparaged men for acting as if their flu symptoms are more severe than those experienced by women. As it turns out, the men have been right all along.

According to a study by researchers at the Johns Hopkins Bloomberg School of Public Health, women possess a natural protection against the flu: estrogen. The female sex hormone has been shown to hamper the replication of many types of viruses, including influenza, HIV, Ebola, and hepatitis.

The difference in disease intensity between men and women is dramatic, with women showing a nearly 1,000-fold reduction in viral replications than their male counterparts.

The next time you see a man seeking sympathy because of the severity of his flu symptoms, consider offering kindness; he may actually have a legitimate complaint.