Most women rely on thong underwear to prevent panty lines and avoid the awkward scrunching that occurs with full-fledged briefs. But that doesn't make your much loved thongs 100 percent healthy to wear at all times, according to Jill Rabin, M.D., professor of obstetrics and gynecology at Hofstra North Shore-LIJ School of Medicine in New Hyde Park, New York.
That's because the piece of fabric that constitutes a crotch tends to be very narrow, Dr. Rabin explains. When you move around throughout the day, that fabric can easily shift between your rectum and vagina—bad news if that fabric is carrying rectal bacteria or viruses, which could infect your vagina or your bladder. The risks only rise with ill-fitting underwear. When it's too big or too small or particularly skimpy, the fabric is even more likely to shift around.
Consider slipping on fuller briefs when you have any of these additional infection risk factors:
1. You don't wear cotton underwear. Artificial fabrics like nylon trap moisture. Cotton lets air circulate around the vagina, which helps your skin breathe and maintains the healthy acidity that fends off vaginal infections. If you must wear silky-feeling fabrics, go for bikinis to avoid icky, uncomfortable outcomes.
2. You wear workout clothes all day. Tight clothing like spandex leggings can interfere with air circulation. But damp, tight clothing is an even worse offense: It can foster bacterial growth that disrupts your vagina's healthy balance. Bring a fresh pair of underwear (and pants if you're prone to swamp ass) to keep things fresh after exercise.
3. You're wearing a short skirt. If your skirt hikes up when you sit down on, say, a taxi seat, you're better off in a bikini brief. Go bare-assed in a public place, and you could sweep up bacteria and viruses that rival those in a portable toilet.
4. You're prone to yeast or bacterial vaginal infections. If you're in an exclusive relationship with your thong collection and you've never had a problem, your immune system might be especially stellar. But if you do get yeast infections or UTIs, your thongs may be to blame, and you might want to swap them out for bikinis.
5. You're pregnant and prone to infection. Pregnancy compromises the immune system a smidge, which can increase your risk of vaginal infections and ultimately pose risks for your baby. Besides, when you're walking around with 30-plus extra pounds, do you really need a yeast infection to boot? Don't risk it by wearing thongs.
6. You shower next to never. Daily washing with gentle soap can help reduce skin and vaginal infections. If you don't hose down at least once a day, you'll raise your infection risks.
7. You change your tampons next to never. While it's unlikely that your thong could make your tampon string rub up against your rectum, then drag it forward to infect your vagina, it's not an impossible scenario. It could happen if you change your tampon less frequently than you change your undies (which gives the string more time to sweep up bacteria). To avoid infection, use the lightest tampon for your flow and change it when it feels no more than two-thirds full—regardless of your underwear, Dr. Rabin says.
8. You wear sanitary pads. Pads (including the genius ones designed for thong underwear) can increase the bacteria count in your vagina — particularly if you change it infrequently, Dr. Rabin says. Any change in your bacteria count could be bad news for your vagina and bladder.
9. You douche or use personal deodorants. Dr. Rabin recommends against using these products because they can mess with the natural acidity and balance of bacteria in the vagina, which for the record, can clean itself. If you still swear by a product that makes you feel squeaky clean, know that it can compromise your immunity. To minimize risk of infection, go for fuller-cut undies for extra protection from environmental hazards.
10. You leak. Two out of every five women under 60 deal with bladder leaks whether it's from sports or from holding urine in too long, according to Dr. Rabin, who's also the co-author of Mind Over Bladder. When even a few drops of acidic urine hangs out in the crotch of tight-fitting thongs, it could irritate sensitive skin and cause a rash that brings you back to diaper days. (Eek.) Talk to your doctor if you deal with leakage on the regular.
11. You don't use condoms and have multiple partners. This risky move sets you up for infection on its own. Thong underwear could cause additional irritation, increasing your susceptibility to contracting an STI.
12. You're sick. That means your immune system is already compromised (and quite busy stopping your running nose or fever). This could increase your risk of infection from other germs creeping around the crotch area, which will only make you feel worse.
13. You're going swimsuit shopping. You definitely want to go with full-fledged bikini briefs in this case, Dr. Rabin says. This way, you'll protect yourself from germs left by the last eight women who tried on, then discarded the bikini bottoms in your try-on pile.
This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.