What Is Period Underwear?

Medically Reviewed by Brunilda Nazario, MD on January 18, 2023
4 min read

There are lots of types of period products. As you search for the one that works best for you, you may come across period-proof underwear. Anyone who menstruates can use these undergarments to comfortably protect themselves during their cycle.

These absorbent underpants have multiple layers of microfiber polyester. They look like regular underwear, but they’re designed to keep moisture away from your skin as they soak up menstrual blood.

The fabric in period underwear contains a moisture-wicking fabric made up of thousands of small filaments. These fibers trap blood or other liquid to keep it from leaking onto your clothes. The outer layer usually includes nylon and Lycra, and is then finished with a liquid-repellent film.

When you start your cycle, you’ll use period underwear to catch the blood. You’ll put them on just like a regular pair of underwear.

They’re usually made with a moisture barrier designed to keep you feeling dry. Plus they have another layer to prevent leaks.

Pick one that fits and feels comfortable, not too tight or too loose. With some types, you can also wear it to hold a pad in place at night. That can give you extra protection from leaks or stains. 

But it’s important to change and clean period underwear every 12 hours, or more often if needed. Many types have an antimicrobial layer to help get rid of odor. But switching them out regularly will also help keep you fresh.

Washing instructions will differ based on the type and brand you use. Read the instructions before you clean them.

Anyone with a period can use period underwear. But it’s important that you know what to expect if you’re not used to free bleeding, which is a term used to describe when someone menstruates without the use of tampons or other common period products.

Period underwear doesn’t stop the flow of your period blood. If you use it, you’ll feel the flow of menstruation, which can be unsettling for some people at first.

Some women also use period underwear alongside other products, like tampons or menstrual cups, to add another layer of protection. But you can use period underwear by itself. Some brands come in different levels of absorbency, so you can choose a pair that works best for you on a particular day. Most pairs of period underwear are highly absorbent. But if your flow is heavy, it’s a good idea to check from time to time and see if you need to change them.

Yes, as long as you use and wash it correctly. You can hand-wash period underwear, or throw it in your washer and choose the gentle or delicate cycle. 

To clean period underwear, you should:

  • Wash it by itself. Don’t throw it in with your other clothes or items like towels or socks.
  • Use a mild, dye-free detergent.
  • Don’t use fabric sheets or softeners, especially scented ones.
  • Make sure there’s no soap residue after washing. Put it through an extra rinse so it doesn’t irritate your skin. 
  • Let it air-dry.

Unlike disposable period products, you can use period underwear more than once. The cost of period underwear varies, depending on the type and brand. Some cost around $8 a pair, while others are over $60 a pair. If you wash them according to the instructions, they can last from around 6 months to about 2 years.

But period underwear isn’t just designed to be used when you’re having a period. You can use it between periods to catch discharge if you have urinary incontinence (leak urine by accident), or for bleeding you may have after giving birth (postpartum).

There’s no “right” period product to choose. Your decision should be based on your personal comfort and well-being.

A study found that some period underwear contains high levels of PFAS (per- and polyfluoroalkyl substances) on its outer and inner absorbent layers. 

Also known as “forever chemicals,” PFAS are a group of long-lasting chemicals used to make products resistant to heat, oil, stains, and water. 

You can often find them on things like furniture, plastic food covering, and nonstick cookware. They’re concerning because experts found that PFAS don’t break down easily in the environment. They can seep into your body and build up inside you. 

Long-term exposure to high levels of PFAS may cause you to have health issues like:

  • High cholesterol
  • Changes in your liver enzymes
  • Lower birth weight for your babies
  • Increased risk for some types of cancers
  • Pregnancy complications like preeclampsia
  • Reduced vaccine response in children

Before you buy period underwear, check with the maker or product labels to see if they mention “PFAS-free.” Avoid those that say “PFOA-free,” as this means it’s free of some PFAS chemicals, but not all.