Wait, just hear us out - wearing underwear for a second day may not be that bad Share Wearing clean underwear every day is one of the first rules of hygiene most of us were taught as children. But that doesnât always materialise when you are an adult. Reasons may be anything from skipping laundry day, or having gone to a party at a friendâs or sleeping over at a friend's unplanned without bringing an overnight bag. We have good news for anyone whoâs skipped a laundry day: As far as health is concerned, itâs not a huge issue to wear the same pair of underpants for 2 days in a row, says dermatologist Scott Kasteler, speaking on Greatist, a health and fitness website.