Underwear is the last line of defense between your ladybits and the outside world, but the wrong pair can wreak havoc on your vaginal health. Here are a few bad habits that can cause problems:
1. Wearing the same pair post-workout
When you change out of your sweaty gym shorts, make sure you also grab a fresh pair of undies. "Yeast and bacteria love a warm, moist, dark environment," says Octavia Cannon, DO, a board-certified ob-gyn, co-owner of Arboretum Obstetrics and Gynecology in Charlotte, North Carolina, and vice president of the American College of Osteopathic Obstetricians and Gynecologists. Sweaty briefs are a breeding ground for fungi and bacteria, so change out of them ASAP.
2. Choosing fancy fabrics
Granny panty devotees, rejoice: Breathable cotton is the best fabric choice for everyday wear. "If you choose undies made of other fabrics, select a cotton crotch whenever possible," Dr. Cannon says. If you have a few cute-but-impractical pairs you simply can't part with, just save 'em for special occasions, and rock the moisture-wicking fabrics on a daily basis. Letting your vag breathe will reduce your risk of infections.
3. Getting lax about laundry
We're all guilty of occasionally taking a pair off the top of the laundry pile and giving them a repeat performance. But unless they're seriously spotless, you're better off with a fresh pair. "Please wear your undies only once before washing them—especially thong underwear," Dr. Cannon says. Just like sweaty underwear, a dirty pair can breed bacteria and put you at risk for infections. No clean undies in the drawer? It is OK to go commando if you're comfortable with it.
4. Swearing by thongs
If you can't figure out why anyone would want a perma-wedgie, you don't need to worry about this. But if you prefer thongs, be aware they can transfer E. coli bacteria from your crack to your vagina. "Think about where the string slides when you sit down in a thong," Dr. Cannon says. (Eww.) If you can't deal with panty lines, or just find thongs more comfy, it's OK to keep them in rotation—but find a cotton pair that fits well, change them daily, and don't sleep in them. And if you're especially prone to yeast infections or other vaginal infections, consider switching to briefs or boy shorts.
5. Sizing down
Underwear that causes a muffin top or camel toe is probably too tight—and that can lead to health issues. "If your panties are leaving marks on your skin, you are putting yourself at risk for vaginal infections and rashes," Dr. Cannon says. Underwear sizes vary from brand to brand, so buy based on fit and comfort, not what the label says.
6. Using scented detergent
If you've had a few infections or rashes recently, check the label on your laundry detergent. "Consider using a fragrance-free detergent, and eliminate dryer sheets with fragrance," Dr. Cannon says. (Ditto for scented soaps and body washes, BTW.) No one expects your undies to smell like a bouquet, so skip any products that irritate the super-sensitive skin down there.
This article originally appeared on Seventeen.com Minor edits have been made by the Cosmo.ph editors.