Your butthole might need a break.
Guille Faingold / Stocksy
In 1999, a certain blonde-haired R&B singer released an entire song about his love of thong underwear. It was an asinine song, but an entire generation of tweens (like myself at the time) ran out, purchased flimsy undergarments, and walked around the mall on weekends with string between their butts. Even though your friend was probably three when that song came out, she inherited a taste for both 90s music and butt floss. You were okay with her strange thong affinity until you discovered homie isn't just wearing them around the mall—she sleeps in them too. Thongs all day and all night? Do panty lines even matter in the dark? Even so, it can't be healthy.
While cotton full-coverage underwear is a favorite among gynecologists, sleeping in any underwear at all is known to increase the temperature and moisture in and around the vagina. "The vagina certainly does need to breathe and that can be accomplished by sleeping without underwear," says Ronald Blatt, OB/GYN, chief surgeon and medical director of the Manhattan Center for Vaginal Surgery. "This will cool you down, air you out, and may prevent yeast infections which usually happen in moist, and warm areas of the body."
So if you're best off without any underwear at all, logic would imply your friend's lacey thongs aren't designed for 24/7 use. But because your state of mine is also important when it comes to sleeping soundly, don't go commando unless you feel totally comfortable doing so, Blatt says.
The Worst That Could Happen:
Additionally, though thong underwear seems like it's wedged securely in your butt, it moves around quite a bit when you're sleeping. "The thin piece of material of the thong moves around as you naturally position yourself while asleep and it could possibly transfer bacteria from anus to vagina or urethra. This may cause infection," Blatt says. Plus, any underwear made of lace or synthetic material is less effective at absorbing moisture. And that moisture creates a desirable breeding ground for bacteria and infection, he adds.
All the movement can even create tiny tears in the skin where microbes can nest and breed, Blatt says. These tiny wounds are the perfect place for microbes to settle. "[The thong] may also be depositing colonic bacteria into your vagina or urethra," Blatt says. And this colonic bacteria—for anyone that's interested—includes E. coli that can contribute to bladder infections and bacterial vaginosis. If these are left untreated, they can even evolve into pelvic inflammatory disease and result in infertility.
What Will Probably Happen:
We don't know your friends vaginal situation, quite frankly. But Blatt says that as long as she doesn't have a history of frequent infections, she should be fine. That said, frequent thong wearers are at greater risk for irritating their hemorrhoids, if they already have them. "Wearing thongs that are too tight in the inseam can cause rashes or irritation and even cuts and scratches," Blatt says. Thongs can also cause skin tags—those piles of extra skin that some people get on their neck, chest and back. "If you do choose to sleep in a thong, select a cotton pair," Blatt says. "Cotton fabric is better for your vaginal health."
What to Tell Your Friend:
We're not sure why your friend likes sleeping in thongs. But if it's important to her, suggest that she mix up her repertoire with some regular cotton undies or even a loose fitting boxer brief. Tell her that cotton briefs are breathable, and comfortable, and some full-coverage skivvies will give the skin around her vagina and anus a break.
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