Newsflash: you just missed National Underwear Day. Started by an underwear retailer called Freshpair, the holiday has been celebrated on August 5th since 2003. Sure, you might think this is a silly campaign to sell panties, but we probably don’t talk about our undies enough.

Example: Did you know that the wrong pair of undies during exercise can up your risk of infection? Or that thereis a time when going commando is a good idea? Keep reading.

In honor of this very important holiday (kidding, kind of), we rounded up 6 underwear rules every woman should live by, with the help of top experts.

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Let her breathe
Not only is tight-hugging underwear often uncomfortable when worn for long periods of time, it’s also not the healthiest situation for your vagina because it limits airflow. And just as important as well-fitting undies are those made with the right material.

“Cotton undergarments are the best due to their breathability,” explained Dr. Melissa Goist, an ob/gyn at The Ohio State University Wexner Medical Center. “Synthetic fabrics tend to hold onto moisture, possibly causing skin irritation.”

Though cotton is likely your gyno’s first choice in fabric, it sometimes lays lumpy and bumpy under your clothes. But fear not, there are close runner-ups.

“Panties made of things like polyester, nylon, Lycra or Spandex sometimes have more stretch and lay nicer under clothing and still come with that cotton crotch,” added Dr. Melissa Piliang, a dermatologist at the Cleveland Clinic.

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Use a skin-friendly laundry detergent
Treat your skin down there as sensitively as possible, our experts advise. “I like a hypoallergenic detergent, one that’s made for sensitive skin, free of dyes or perfumes,” Piliang said.

You should also avoid using bleach on laundry day if your knickers are involved.

“You never want to bleach your panties,” warned Piliang. “Not only does it break down the fibers of the cloth and wear your underwear out faster, it can also expose you to chemicals when it interacts with elastic that can cause an allergic reaction on the skin.”

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Change them (duh)
Seems obvious, right? But in addition to changing them daily, you should avoid sitting too long in a damp pair on a sweaty summer afternoon—or worse, post-workout, if you’re prone to yeast infections.

“Underwear can trap moisture,” said Goist, adding that bacteria and yeast “love to multiple in a warm and wet environment.”

Whether you’re prone to infection or not, use dampness as a cue to send your undies to the laundry basket. “If the discharge is bothersome—you can feel the wetness or moisture—then you should get a new pair,” Goist added.

It’s also important to note that lingerie has a shelf life: “Once the elastic is failed and they’re not staying in place and causing extra rubbing and shifting around, it’s time to throw them out and get some new ones,” Piliang said.

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Think before you thong
“Due to the nature of the design, thongs can potentially promote transmission of colon bacteria towards and into the vagina,” said Goist. “This potentially will disrupt the normal bacterial milieu and increase the risk of vaginal and urinary infections.”

And if you’ve ever had the displeasure of working out in a G-string, you may want invest in a panty that’s designed for exercise to keep in your gym bag.

“Lots of sports gear incorporates that element these days,” Piliang said. “Bras, socks, shorts, and underwear now come in a kind of nylon wicking material that will absorb the sweat and pull it away from the body so it can dry. The last thing you want to do is sit there in a soaking wet pair of underwear.” (Again, especially if you’re prone to yeast infections.)

A good general rule of thumb: limit your thong use to when you really need to wear them (we’re looking at you, Little Black Dress).

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Study the stains
Grossed out? Don’t be. You don’t have to get that up close and personal with your unmentionables, but you should be paying attention because your discharge can tell you a lot about your health and whether things are working as they should down under.

“Normal is different for everyone,” Goist said. “Often an off-white discharge is not concerning, but if you have an odorous discharge or notice new blood—and you are not about to menstruate—you should call the physician to discuss.”

Know when to go bare
You’ve probably wondered whether going commando is safe for your lady bits. Turns out, it is—if you’re comfortable sans that little layer between you and, well, everything else.

“Commando is safe as long as there is no other fabric causing friction on the vulva,” explained Goist.

But there are a few instances where skipping underwear is not in your best interest (and not just when you’re in a dress on a windy day).

“First of all, wear undies when you work out,” said Goist. “If you don’t the friction from the workout can cause major discomfort and soreness.” She also advises never to skip underwear when wearing jeans to prevent painful chafing that can lead to sores—and then possible infections. Yeeouch!

Your safest bet is relaxing undie-free at bedtime. In fact, it’s sometimes a healthier option at night. “If a woman is having vaginal problems, discharge, or pain then often sleeping commando is encouraged,” said Goist, who gives the go-ahead for snoozing easy and breezy in a nightgown or your birthday suit.

Bottom line: “There are many different types of panties these days, and somewhere you’re bound to find something that feels both nice on your skin and comfortable on your body,” concluded Piliang. Whether you’re a cheeky gal, lacy lady, boy-short lover or full-coverage fan, always practice these safe and sanitary undie habits.

This article originally appeared on Health.com.