It is known that you have to change your underwear every day and wash them before wearing them again (otherwise...yuu). What about the "lifespan" of underwear, from a health perspective, is there a time when you should throw out the old ones and buy new ones?

The answer is not as simple as you might think, gynecologist Taraneh Shirazian told Health. No medical evidence shows that wearing old underwear is a risk factor for a particular vaginal condition, says Dr. Shirazian. But in terms of comfort and reducing the chances of any problems — like an allergic reaction or infection — you should replace your underwear regularly, she advises.

Philip Tierno, a professor of microbiology and pathology and author of "First Wear a Mask: A Doctor's Guide to Reducing Risk of Infection During a Pandemic and Beyond," agrees that underwear does not have an expiration date. But the inners may be "mechanically dysfunctional" — in other words, they have holes or the material is damaged — so it's time to replace them.

What can happen if you wear old underwear? The risk is not high, but a pair of underwear that no longer fits properly can cause infections. If the undergarments are loose, they can irritate the skin and increase the risk of infection.

"When you're choosing underwear, be careful about details such as materials, colors and chemicals," suggests Dr. Shirazian. She recommends cotton material because it keeps moisture out and prevents infections. On the other hand, fabric synthetics such as nylon retain moisture and do not dry easily, causing irritation and infection.