Choosing what underwear you’re going to buy usually comes down to two things: comfort and style. Sometimes we go for both, other times, one completely over the other. But you’d be remiss to not consider your lady parts when investing in new underthings.

The type of undies you choose, while not likely to be a sole cause of a bacterial or yeast infection, can contribute to irritation and chafing, and worsen preexisting problems in the area, Alexander Chiang, M.D., assistant clinical professor in the department of obstetrics and gynecology at the David Geffen School of Medicine at UCLA, tells SELF. Certain materials trap in heat and moisture, affecting your comfort and the overall balance of good and bad bacteria. Others simply may be uncomfortable and cause skin reactions and chafing. Here’s how to select your skivvies.

Cotton is what most experts recommend, because it doesn’t hold moisture in.

The classic advice when perusing for panties is to choose cotton over anything else. “Generally, cotton underwear is recommended since it has a natural moisture wicking and drying effect. And it’s cheap,” Chiang points out. Silk is more expensive, and some lacy cuts can be irritating. So chances are cotton will give you the most comfort for your dollar.

The oft-dispensed advice to avoid synthetics might be off the mark, especially if you work out a lot.

Other materials that wick away moisture can be just as effective as cotton and still preserve the vagina’s natural environment. “There is no data at all anywhere to suggest that cotton is better than synthetics,” Jennifer Gunter, M.D., an ob/gyn and pain medicine physician, tells SELF. “Occlusive material (think plastic) can definitely affect moisture levels and the microclimate, so latex rubber panties (like the ones that Miley Cyrus wore) are not the best idea for any extended period of time, but that isn’t what most people wear all day.” (Does anyone?) When it comes to choosing between cotton or something like polyester or silk, science doesn’t really reveal a clear winner.

In fact, wicking underwear that’s made of synthetic materials (like these ones from Sweaty Betty) may be a smarter choice when you know you’re going to sweat a lot. “Cotton underwear will feel wetter after a workout, so if you are the type of person who sweats a lot, you may be more comfortable in the synthetics made to wick the moisture away,” Gunter says. If you are prone to yeast infections or have yeast overgrowth, keeping the area dry is especially important—yeast thrives in warm, wet environments.

That said, synthetic fibers aren’t for everyone.

The case against synthetics? “Some people can get skin sensitivity (dermatitis) in general to synthetic materials,” Chiang says. “But if they aren’t sensitive, I see no reason not to wear it all the time.” He also adds that typically we shouldn’t have to worry about the materials in our pants, either. Our clothing in general is less likely to cause irritation since it’s on the outside, though for some, it does make an impact.

And here’s the deal with thongs.

Wearing a thong that’s too tight can cause some rubbing and irritation (both on your front and back ends), but Gunter reassures that opting for butt floss over boy shorts isn’t going to do anything to that would increase the chance of infection, like alter the pH of your vagina. “A tighter thong style doesn’t change the pH or the microclimate of the skin,” she says. If your thong is rubbing you the wrong way, a cotton style might be more comfortable simply because it’s got more give.

No matter what material you’re wearing, it’s never a good idea to sit around in damp underwear.

“The choice of underwear is far less important versus what you do if you are soaking wet post-workout,” Gunter says. “If your underwear is soaking wet, it could lead to chafing and that is frequently misdiagnosed as yeast.” If you’re wet and can’t shower and change clothes immediately, consider at least toweling off and changing your underwear. Same goes if your underwear has become really wet or sweaty for any other reason. “If they’re not soaking wet and you don’t have a skin irritation issue, then you are probably fine.”

Bottom line: Choose what keeps you dry and feels good to your bottom line.

It really comes down to personal preference. “Some people prefer the feel of some fabric or dislike the feel of others,” Gunter says. “It’s really all about what you like, as long as it isn’t plastic. Plastic or latex underwear is a definite no.” Hopefully Miley gets the memo.