We consulted two experts who know a lot about periods and absorbent hygiene, respectively: San Francisco–based obstetrician-gynecologist Jen Gunter, MD, who writes a column for The New York Times (Wirecutter’s parent company) called The Cycle; and Mandy Fader, RN, PhD, a professor of continence technology at the University of Southampton in the UK. We also spoke with Rolf Halden, director of the Biodesign Center for Environmental Health Engineering at Arizona State University, and with University of Notre Dame nuclear physicist Graham Peaslee (whose lab tested period underwear sent in by a columnist for the Sierra Club magazine) about chemicals found in treated garments, including some period underwear.

Though period underwear can hold more than a tampon’s worth of fluid, we think most people will find it is best used as a backup method of leak control rather than as a first line of defense in managing menstrual flow. If you find yourself experiencing or worrying about leaks during your period, or if you’re anticipating the start of your menstrual cycle but you’re not sure of the exact date, a pair of absorbing undies can provide peace of mind and will be more comfortable to wear than most pads or panty liners.

If your periods are generally light, or if you prefer to avoid tampons or a menstrual cup on light-flow days (meaning on days you’d need to change a pad or tampon only about twice a day, according to some studies, though definitions vary), period underwear can be a good option. If you really hate wearing pads, tampons, or a menstrual cup, period underwear may be right for you as a primary collection method. But because period underwear is roughly $10 to $44 a pair—and since most people would need to use two to four pairs per day—using only period underwear could get expensive if you want to avoid having to do laundry every day of your period. And it could mean having to carry bloody underwear around with you.

Despite its absorbency, period underwear isn’t a good solution for urinary incontinence. Menstrual fluid flows at a lower volume and a slower rate than pee, and most pairs of period underwear aren’t absorbent enough to handle urine from a leaky bladder (there are a number of specialized undies for that, including an option made by the same company as Thinx, though we haven’t tested these). Commenters on Reddit have reported mixed results when using period underwear rather than traditional menstrual pads for postpartum bleeding.

In short, yes. Or, period underwear is as safe as most other things we place against our skin. Despite a recent report raising alarm about potentially harmful chemicals in pairs of Thinx, experts we consulted about perfluoroalkyl and polyfluoroalkyl substances (PFAS) in treated garments—including the researcher whose lab identified these molecules in samples sent in by a columnist for the Sierra Club magazine—said that concerns about such substances in period underwear are largely overblown.

Almost every fabric that is designed to be water-, stain-, or wrinkle-resistant contains PFAS. And these substances aren’t just in clothing: “These chemicals are in everything from drinking water to dental floss,” says Rolf Halden, PhD, who runs Arizona State University’s Biodesign Center for Environmental Health Engineering. “It’s virtually impossible to escape them,” agreed Graham Peaslee, PhD, whose team found PFAS in pairs of Thinx underwear that a columnist had sent in. (The results of this testing haven’t been independently verified.)

In an emailed statement, Thinx CEO Maria Molland said that “if any unregulated PFAS chemicals are ever found in our products, we will move swiftly to remove them.” The company provided Wirecutter with—and has since posted online—copies of third-party safety testing it has commissioned. (The results of this testing, too, haven’t been independently verified.) “Thinx tested for what they were told to test for, which was the list of European-regulated PFAS,” Peaslee explained. “The short-chain PFAS [we] found in the panties are not yet regulated in Europe and so were not on the testing list.”

The experts we talked with suggested that PFAS in period underwear pose less of a personal threat compared with PFAS found in food wrappers and drinking water, which may be ingested. Obstetrician-gynecologist Jen Gunter told us she’s “not concerned about the chemicals in underwear you wear a few times a month.” Singling out period underwear, she said, isn’t entirely fair—even given its proximity to genitalia. “Yoga pants, for example, are worn by millions more women on a near-daily basis. If we’re going to look at dermal absorption, something like yoga pants, which are made from similar materials as menstrual underwear, would be a better bet to scrutinize.”

We searched for period underwear based on the following criteria:

• Leak prevention: We focused on period underwear designed to collect (and contain) menstrual fluid, rather than just hold a menstrual pad in place. Different styles of period underwear hold different amounts of fluid, from one light tampon’s worth to two regular tampons’ worth. We selected underwear on the higher end of that range to test whether it worked as a tampon replacement.
• Wide range of sizes: We chose brands that offer underwear in sizes XS through 4XL, favoring brands that offer the full size range for all their styles.
• Style variety: Period undies are often pretty cute! We favored brands that offer a range of cut and color options, from thongs to high-waisted briefs and subdued to colorful. Even if you typically prefer plain panties, you might consider getting period underwear that looks distinct so it will stand out in your drawer and be easy to find when you need it.
• Availability: We considered underwear only from companies that had most of their offerings in stock at the time of testing.

A panel of six testers (including, at different times, both authors of this review), who wear sizes ranging from XS through 2XL, ordered underwear from Bambody, Dear Kate, Hesta/Rael, Intimate Portal, LunaPads, Knix, Ruby Love (formerly known as PantyProp), and Thinx. Testers chose their favorite colors, styles, and cuts, ordering from brands that had their preferred pairs in stock.

We wore each pair for a full day and then laundered it, at least twice, to evaluate comfort and fit. Most testers worked out wearing the undies, using them while doing yoga, jogging, or lifting weights. (Both authors of this review wore period underwear day and night during our periods.)

In a nonscientific test at our kitchen counters, we evaluated the amount of fluid that each pair of underwear could hold by pouring water into the crotch, a quarter-teaspoon at a time. Pairs from all of the brands we tested were able to hold more than their rated amount (at least 3 teaspoons, or about two tampons’ worth of liquid) with negligible spotting.¹

Our pick

Dear Kate period underwear

Superior comfort, plenty of styles

Dear Kate underwear tied with Thinx for absorption and bested that brand in comfort. Dear Kate undies come in a wide variety of styles, from high-waisted to thong, and in a range of colors, from pastels to brights.

Buying Options

Buy from Dear Kate
(starts at $32)

Although the pairs of period underwear we tested from the three brands we recommend all performed equally, testers rated Dear Kate underwear as the most comfortable to wear of all the brands they tried. Dear Kate undies come in a variety of styles and colors, and because they employ layers of absorbent fabric in the gusset to contain leaks, they don’t have the crinkly-feeling waterproof lining that our other picks have. We found that Dear Kate period underwear held up well after several washes and maintained vivid hues.

We’ve noticed some stock issues with Dear Kate that the company attributed to increased demand. We consider this a flaw—but not a dealbreaker. For the comfiest, most stylish pair of leakproof undies we’ve tried, we think it’s worth the wait for a restock of your preferred style, color, and size from Dear Kate.

Price (per pair): $32 to $44 at the time of publication
Available sizes: XS (from 32-inch hip) to 3XL (up to 58-inch hip)
Waterproof lining: No
Return policy: 30 days; exchanges are free, customer pays return shipping for refunds

Runner-up

Thinx period underwear

Easier to return, run small

Though Thinx undies come in a range of styles and performed as well as the Dear Kate period underwear, they tend to run small and tight. The Thinx underwear’s waterproof lining is also more conspicuous, testers said.

Buying Options

Buy from Thinx
(starts at $32)

Thinx period undies are as effective as those from Dear Kate, and they come in roughly the same number of colors and styles. They’re comparable in price, too. Testers didn’t rate Thinx as highly as Dear Kate in terms of comfort, largely because the crotch of Thinx undies has a waterproof lining that can at times feel crinkly. Compared with Dear Kate undies, the Thinx panties we tried felt more like “period underwear.” We also found they ran small, even in the company’s suggested sizing. But they held up well after several washes.

We’ve noticed occasional stock issues with Thinx, but we did not have trouble buying our preferred styles, colors, and sizes during our test period.

Price (per pair): $24 to $42 at the time of publication
Available sizes: 2XS (from 33-inch hip) to 3XL (up to 49½-inch hip)
Waterproof lining: Yes, polyurethane laminate
Return policy: 60 days for free exchanges and returns

Budget pick

Bambody period underwear

Effective and inexpensive, not as durable

Bambody undies are as effective as Dear Kate and Thinx undies when it comes to absorbing menstrual fluid, but they start to fade and discolor after 15 or so washes. Like Thinx, they also run small and have a somewhat noticeable lining. Bambody undies come in fewer styles and colors than our other picks, but they’re less than half the price.

Buying Options

Buy from Amazon
(starts at $10)

$30 from Bambody

Expect Bambody period underwear to fade and become discolored more quickly than Dear Kate or Thinx undies. That flaw aside, they are as effective as pairs from the other brands we recommend, but they cost about half the price. Like Thinx undies, Bambody panties rely on a waterproof lining that our testers found somewhat noticeable, and they tend to run small.

We didn’t encounter any stock issues with Bambody underwear during our test period. It’s easy—and free—to return “new and unused” undies to Amazon. (Bambody won’t share its specific refund policy.)

Price (per pair): $10 to $15 at the time of publication
Available sizes: XS (from 33½-inch hip) to 4XL (up to 51-inch hip)
Waterproof lining: Yes, polyurethane laminate
Return policy: 30 days for free exchanges and returns (Amazon’s policy)

We found the pairs from Dear Kate, in particular, to be stylish and comfortable, at least for low-key activities like lounging and sleeping. And we liked wearing some other pairs, like this boxer brief from LunaPads, nearly as much. Testers appreciated how slim period underwear felt compared with other backup methods like pads and liners. And although we ultimately think period underwear is not the best primary collection method for most people, for several reasons, we found it to be useful for backup leak protection and, under specific circumstances, effective when worn alone.

Both authors of this review tried wearing period underwear alone—not as a backup—during our periods, and came to similar conclusions. Although it’s a little strange free-bleeding into undies at first, period underwear usually does a good job of keeping menstrual fluid from leaking, as long as you change it frequently enough (in our experience, every two hours or so in the middle of a heavier period). We both found wearing the underwear alone, as a primary collection method, particularly pleasant and freeing while hanging out at home on lighter days, because changing the undies was as easy as tossing the dirty pair into our laundry piles. Panel testers who regularly experience lighter flows reported no leaks while using period underwear on its own. One tester who regularly has extremely heavy periods, though, experienced some degree of leaking with all but one pair worn as a primary collection method for more than two hours. (Even though the comfy and secure LunaPads boxer briefs did not leak, they did turn into a soggy, regrettable mess after four hours of heavy flow.)

Sitting around in blood-soaked undies might sound gross, but period underwear is actually pretty comfy. The pairs from all eight brands we tested stayed acceptably dry against our skin, even after hours of collecting menstrual fluid. Most brands and styles are made using synthetic fabrics, though Dr. Jen Gunter told us that materials are more a matter of personal preference than of health. “There’s no association between cotton or synthetic underwear and yeast infection.”

Dear Kate underwear doesn’t use a waterproof lining, while Thinx and Bambody both do. “The absorbing section was thick and stiff, and I felt aware of it especially while moving around,” one tester said of the Thinx pair they tested. “Less so than a pad, but still very much there.”

Testers found that blood easily washed out of all the pairs they tested. After 15 or more test washes, the Bambody underwear began to look raggedy, whereas the Dear Kate and Thinx undies appeared fine.

Companies that sell period underwear are fairly secretive about their absorbent technologies. Although period underwear hasn’t been the subject of peer-reviewed studies, according to Gunter there’s no evidence that it’s any less safe, sanitary, or effective than disposable menstrual pads.

As much as we appreciate the existence of period underwear, we didn’t find it to be a suitable replacement for a pad, tampon, or menstrual cup. Pairs of period underwear are costly up front compared with other collection devices and—unless you are committed to mid-period laundering and using each pair for several years—ultimately more expensive than most pads, tampons, and cups. Plus, they can be difficult to change when you’re away from home. If you have a particularly heavy flow, you may need to change pairs more often each day, adding to the total cost. And using period underwear in place of pads, tampons, or a cup may also require that you do more (and potentially messier) laundry.

Over 24 hours during the middle of one tester’s period, when her flow was heaviest, she went through five pairs—about $100 in underwear. There aren’t guidelines on how often people should change period underwear: “People should go with their comfort level,” Gunter told us. If you wear a pair for too long, your only real risk is a leak or discomfort.

If you do decide to use one of our period underwear picks as a primary collection method, you can estimate how much you’d need to spend to be covered for a single day by dividing however many tampons you typically use in 24 hours by two, and then multiplying by $40 (for our top pick and runner-up), or $15 (for our budget pick, which can be bought in a more-economical pack of three).²

The reality is, it can be hard to know when to change period underwear. Unlike pads or tampons, which show blood and/or feel full, period underwear doesn’t reliably offer the same tells. The gussets lining the crotch on all of the pairs we tested are black. And, even when full, the layers of absorbent fabric don’t visibly bloat like a pad would, plus they feel dry to the touch.

Further (and perhaps most annoyingly), changing the undies while you’re out of the house can be cumbersome, particularly when you’re doing so in a cramped restroom stall. And then you need somewhere to put the dirty pair. One night, a tester attended a formal fundraising event, her purse stuffed with a backup pair of period underwear and a Duane Reade bag awaiting bloody panties.

Turns out she was following the companies’ best advice for transporting used pairs. “Safely store the garment by folding it in on the crotch area to prevent wetness from spreading and placing it in a pouch or bag,” a Dear Kate representative wrote in an email. “This will keep them from soiling your other items.” A Thinx representative likewise wrote via email to “bring a plastic bag.”

After a few hours of usage, menstrual panties can develop a smell similar to that of a used pad. Although bloggers have reported a menstrual blood smell remaining even after they washed their Thinx, our testers did not find this to be so. Period undies need to be washed with care; instructions from all companies recommend setting the machine to cold water, avoiding fabric softener (which companies say can coat the underwear and prevent them from absorbing properly), and either tumble-drying on low heat or air drying, since heat can degrade the absorbent fabric. Dear Kate notes that you should avoid dryer sheets (which can also impede absorbency). Thinx recommends that you rinse the underwear before putting it in the wash, and air-dry it afterward.

Finally, we found exercising in period underwear doable, though not ideal. Some testers reported minor discomfort due to the extra fabric sewn into the crotch. Overall, the more fluid a pair was said to hold, the thicker its fabric felt compared with that of non-period underwear. As with any item of clothing, we found that fit and feel varied among testers. One reported that all of the pairs she tried produced visible panty lines beneath everyday clothes, and another noted this was an issue only when she wore leggings.

Of all the pairs we tested, those from Knix felt the most like regular underwear: They were notably less bulky than undies from Dear Kate, Thinx, and Bambody, which all have larger absorbent linings. However, testers found that these undies also felt less secure. With less lining and leg-hole elastic, the crotches of these undies tended to shift with movement (not ideal for a garment meant to catch blood). Though Knix undies cost less than Dear Kate and Thinx undies at the time of publication, they’re also not eligible for return.

We didn’t like Ruby Love’s period underwear as much as that from Dear Kate, Thinx, or Bambody (Ruby Love was formerly known as PantyProp). Its pairs are designed to be worn either alone (how we tested them) or with a pad. The absorbent crotch lining of each pair has a sewn-in pocket to hold a pad, which, when left empty, makes for unnecessary extra fabric that some testers found uncomfortable. The company sells its own washable, double-sided pads,³ though Ruby Love underwear can accommodate certain disposable pads, too.

LunaPads period underwear performed fine but comes in just four styles and two colors: black and gray. However, one tester loved the brand’s boxer briefs, finding that they bested Dear Kate undies in comfort.

Intimate Portal and Hesta/Rael underwear felt flimsy and less secure compared with our picks.

We chose not to test Tomboyx underwear—despite its extensive size and style options—based on customer reviews noting sizing issues and leakage.

Liz Thomas contributed reporting.