Finding the perfect underwear-and-leggings combo isn’t easy. Once they pass the squat test and have proven themselves comfortable enough to move in, they also have to pass the no-show test. And thanks to sheer fabrics and panty lines, that’s a lot harder than it seems… unless you decide to nix the undies altogether. But is that a good idea? According to Jodie Horton, MD, an OB/GYN and chief wellness advisor for Love Wellness, it depends on the leggings.

“A warm, wet environment after a sweaty workout can be a breeding ground for a vaginal infection by disrupting the normal bacteria of the vagina and causing an overgrowth of harmful bacteria (like bacterial vaginosis) and yeast,” explains Dr. Horton. She notes that some fabrics and styles encourage this sort of breeding ground than others. “You want to choose materials that allow the vagina to breathe but keep moisture from pooling around your vulva and vagina, which can make it a breeding ground for infections,” she says. With that in mind, keep reading to find out which types of leggings are (and which ones are not) gyno-approved for underwear-free workouts.

The best leggings for working out commando

The cardinal rule of commando workouts? “No matter what type of workout you’re doing or how long you plan to work out, it’s always best to wear breathable, moisture-wicking fabric with a cotton crotch to allow airflow to keep you cool and dry,” says Dr. Horton. As far as crotch-friendly styles go, seamless leggings are likely your best bet, since they’ll “prevent camel toe or constant rubbing of the seams against the labia, leading to swelling and irritation,” she says. If you do want something with seams, look for leggings with a cotton gusset, which is a piece of crotch-reinforcing fabric that prevents leggings from riding up and improves their fit and comfort. Since cotton is naturally moisture-wicking, this will help keep the area dry and well ventilated. Your other option, says Dr. Horton, is to choose a pair of leggings made from one of these breathable fabrics:

1. Polyester and nylon

“These are your best choices for keeping moisture away and keeping the vagina dry even during the sweatiest workouts,” says Dr. Horton. She prefers these materials to spandex, since they can be just as stretchy with a whole lot more breathability.  But it’s worth noting that just because they’re breathable enough to sweat in without underwear, it doesn’t mean you should sit around in them for hours post-workout. “The downside is that synthetic fabric can hold on to fungus, bacteria, and odors,” says Dr. Horton. “So make sure you wash your workout clothes after each workout.”

2. Bamboo

Bamboo is another one of Dr. Horton’s favorite fabrics, and though it’s slightly pricier than some of the synthetic options, it has the added benefit of being environmentally friendly. “Bamboo is moisture-wicking, odor-resistant, temperature-regulating, super-soft fabric,” she says. Shop a few of our favorite pairs here.

3. Silver

Look for leggings that have silver woven into the material. “Silver is an antibacterial agent that helps reduce bacteria buildup and odor in performance fabrics, decreasing the risk for infection,” says. Dr. Horton. Many popular brands, such as Lululemon, use silver in their styles to prevent any post-sweat funk.

4. Rayon

Rayon is a breathable fiber derived from natural cellulose/plant sources. “In general, these fabrics are soft, strong, absorbent, and allow for good temperature control,” says Dr. Horton. Look out for words like Tencel or Lyocell on your labels to know you’re on the right track.

Leggings you should *always* wear underwear with

Spandex may be the leggings world’s MVP in terms of stretch and comfort, but it’s the LVP when it comes to keeping your bits dry during commando workouts. “It isn’t the most breathable fabric option or the best at wicking moisture,” says Dr. Horton.

In this case—and in any other case in which you do decide to wear underwear with leggings—she suggests layering on a pair of breathable underwear (emphasis on breathable), since the only thing worse than one sweaty fabric between your legs is two of them piled on top of each other. “Workout leggings plus synthetic, non-breathable underwear don’t allow sweat to dry,” says Dr. Horton. “It can potentially add another layer that can trap moisture.” Cotton is a great option, but really, any fabric that dries easily will do the trick.

In addition to choosing the right fabric for the underwear you’re exercising in, you’ll also want to pay attention to their style. Dr. Horton suggests opting for bikinis, hipsters, or boy shorts, which will give you full coverage and prevent irritation around your groin. “You want to get something that hugs the body enough to stay in place without riding or bunching up,” says Dr. Horton, adding that seamless styles can prevent chafing as you move. Just be sure to stay away from thongs. “The friction and movement can cause bacteria from your anus to travel along the thong to your vagina and cause a vaginal or bladder infection,” says Dr. Horton. And of course, whether or not you wear underwear when you work out is entirely up to you, but now you’re armed with the knowledge you need to make the best decision for your body.

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