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  • Thinx Hiphugger

  • Aisle Bikini

  • Dear Kate Ada Thong

  • How We Tested Period Underwear

  • Who Should Use Period Underwear?

  • Other Period Underwear We Tested

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Our Favorite Period Underwear of 2021

  1. Best Overall

    Thinx Hiphugger

    Pros

    • Holds two tampons' worth of fluid

    • Doesn't feel too tight

    Cons

    • Absorbs moisture a little slower than others

    Skip to the full review below
  2. Best for Heavier Flow

    Aisle Bikini

    Pros

    • Excellent leak protection

    • Crotch area doesn’t feel as damp as others

    Cons

    • Feels bulky

    Skip to the full review below
Credit: Reviewed / Betsey Goldwasser

Thinx was an all-around tester favorite.

Best Overall
Thinx Hiphugger

Testers—myself included—agreed on one significant high point with the Thinx Classic Hiphugger: It looks and feels like a regular pair of underwear with a slightly thicker area along the crotch, where the absorptive gusset is. The Thinx also felt secure and true to size, which is important: When you’re wearing period underwear, you don’t want any slackness around the crotch, but you don't want it to feel too tight, either.

The pair claims to hold about two tampons’ worth of fluid, which checked out for me. I put them on right after I woke up during a moderate-to-heavy day of my period, then wore them through a work day and to a workout class—about 10 hours in total—and didn’t experience any leaks. Testers had similar results. The Thinx didn’t perform as well in lab tests as some other pairs of underwear—our test pair absorbed the moisture a little slower than some others. But for us, the positive user experience is enough to designate them our top choice.

“I’m obsessed with these,” one tester says. “Seriously, I was so skeptical, but now I'm a convert.”

The Thinx Classic Hiphugger comes in women’s sizes XS to 3XL.

Pros

  • Holds two tampons' worth of fluid

  • Doesn't feel too tight

Cons

  • Absorbs moisture a little slower than others

Woman wearing aisle bikini period underwear with white t-shirt on white background.
Credit: Aisle

Aisle's double-layered system provides the ultimate menstrual protection.

Best for Heavier Flow
Aisle Bikini

Aisle (previously Lunapads, which rebranded and redesigned its products earlier this year) melds old- and new-fangled techniques in its approach to period underwear. In addition to a built-in absorbent gusset, which the brand says holds up to two tampons’ worth of fluid (comparable to most standard period underwear), each pair comes with an “absorbency booster” that purportedly provides another two tampons’ worth of absorption (so, four tampons in total). The absorbency booster is a removable, reusable pad that can be inserted into different pairs of panties—most easily its own, as each Aisle pair features a pocket in the crotch area in which to insert the booster. When you’re done, both the undies and the booster should be rinsed, then machine-washed and dried.

Based on our tests, the bikini briefs live up to its high absorbency claims. Inserting and removing the absorbency booster proved fussy because the pocket is a tight fit (and we didn’t test without it), but once it was in, the pair easily prevented leaks, both in lab and practical tests. It also did a great job of reducing the feeling of dampness that can occur with pads and period underwear, thus providing more comfort and protection for heavier flow days. The Lunapads version of the underwear also used the pad system, but Aisle’s execution is much better. Lunapads’ pad felt more like a piece of cloth that, while effective enough, quickly became damp and sticky-feeling. Aisle’s pad has mesh, which makes it much more breathable. Lunapads also used two thin straps to hold the pad in place, not a pocket, which left more room for slippage.

However, with the built-in absorption of the underwear and the added booster, Aisle panties are some of the most, ahem, noticeable ones we tested. They feel bulkier than most, and provide some discomfort when walking around a lot or exercising. Still, if pure protection is what you’re after, Aisle’s bikini is the right call.

The Aisle bikini comes in women’s sizes XS to 5X.

Pros

  • Excellent leak protection

  • Crotch area doesn’t feel as damp as others

Cons

  • Feels bulky

Credit: Reviewed / Betsey Goldwasser

The Dear Kate thong was the highest-performing one of the bunch.

Best Thong
Dear Kate Ada Thong

We tried out a few different thongs in our tests, and—perhaps unsurprisingly, given that most only promise to hold about one or even only half of a tampons’ worth of fluid—none of them held up that well in tests.

Still, the highest-performing thongs we tried out were the ones from Dear Kate, which claim to be equivalent to about one light tampon. (We tested the Ada thong in the lab and the Hazel and Ada thong in personal tests, because the Ada was out of stock in some sizes when we re-ordered.) Both look like normal thongs—the Ada has lace trim and the Hazel has a more streamlined, athletic look—and have a wider crotch area than other thongs we tested, which helps catch blood.

Some testers—and online reviewers—said they run small, so if you’re between sizes, it’s best to size up. On lighter days, or when you simply must wear a thong when you’re on your period, you want a thong from Dear Kate. One tester used the Dear Kate thong as a backup to a tampon when working out and said it gave her peace of mind and no visible panty line under her leggings.

The Dear Kate Ada Thong comes in women’s sizes XS to XL.

The Dear Kate Hazel Thong comes in women’s sizes XS to XL.

Pros

  • Stylish

  • No visible panty line under leggings

Cons

  • Runs small

  • Only holds a light tampons worth

Related content

How We Tested Period Underwear

The Tester

I’m Sara Hendricks, the health and fitness editor at Reviewed. I have had about 150 periods in my life (give or take a few), and ever since Thinx’s first attention-grabbing ad campaign, I was intrigued, if skeptical, by the claim that a pair of underwear can work as a replacement period product. With the help of Reviewed’s senior scientist Julia MacDougall, a few fellow period-having staff testers, and some blood meal, I put popular period underwear brands to the test to determine the best ones out there.

The Tests

In order to see how each pair of period underwear reacted to a variety of liquids and wear conditions, we devised two different types of tests.

Credit: Reviewed / Betsey Goldwasser

We tested the absorbing powers of each pair of undies.

In the first test, we put 15 grams of water (about the capacity of a super or super-plus tampon) on the crotch of the period underwear to see if the water would leak through or overflow.

Credit: Reviewed / Betsey Goldwasser

We used blood meal to imitate menstrual fluid.

In the second test, we maintained the 15-gram total weight, but replaced 3 grams of water with 3 grams of blood meal, a powdered fertilizer that is partially made up of animal blood, creating a more viscous fluid. That may sound gross, but we wanted to be able to test the period underwear with a solution that looked and smelled like blood; this would help us to assess underwear leakage and cleanliness (as the metallic smell of the blood meal is a pungent one).

Credit: Reviewed / Betsey Goldwasser

There are a lot of pairs of period underwear to choose from.

Once these liquids were prepared, we applied them to the underwear in two different configurations. In the first configuration, the underwear was suspended in mid-air. This setup helped us to get a sense of how quickly the underwear absorbs liquid, as well as how easy it would be for the liquids to soak through or leak along the sides of the panties.

Credit: Reviewed / Betsey Goldwasser

We wanted to see if fluid from the underwear would transfer over to the towel.

In the second configuration, we laid the underwear flat onto a towel, applied the liquid, and then covered the underwear with a second towel, and weighed it down for an hour. This setup gave us a sense as to how any leakage would affect the clothes being worn on top of the period underwear.

Lastly, in between testing each liquid and each configuration, we washed the underwear according to wash instructions. After each wash, we assessed the cleanliness of each pair of underwear, which basically came down to whether or not we could still see or smell evidence of the bloodmeal.

User Experience

Based on the lab testing, we narrowed down the list of period underwear to the top-performing brands—Modibodi, Thinx, Dear Kates, and Luna Pads—and asked four testers to try out a pair from each brand, allowing them to select their own color and style within that brand. They wore the underwear over the course of a month to test for style, comfort, and effectiveness. I also wore each pair of underwear, even the ones that didn’t make the first cut, during my period.

Who Should Use Period Underwear?

Before getting into this, I should make a general period underwear disclaimer: Period underwear works like a pad, in the sense that it collects menstrual fluid once it has left the body. Period panties tend to be slimmer and are less likely to shift out of place than pads, but if you’re typically a tampon or menstrual cup user, you will “feel” your period more with panties than you would with your internal collection method. Because of this, we recommend using period panties for a few things:

  • Wearing on days in the early and later stages of a period, e.g., when it could come or could be finished, but you aren’t totally sure and don’t want to wear a tampon
  • As a backup with a tampon or menstrual cup for peace of mind
  • For people who usually wear pads but want to replace them with something reusable
  • For people who might wear tampons or menstrual cups during the day, but like wearing pads at night

Other Period Underwear We Tested

Product image of Modibodi Sensual Hi-Waist Bikini - Heavy Overnight Absorbency
Modibodi Sensual Hi-Waist Bikini - Heavy Overnight Absorbency

The Modibodi Sensual High-Waisted Brief earned perfect marks in water, blood meal, and towel-transfer tests. It also fared well—though not as well as tester favorite Thinx—in comfort and style. The external layer is made of bamboo and spandex, which provides a soft, stretchy feeling, and the inside is made of merino, spandex, and polyester, which provides absorption for heavy flow days without feeling scratchy. Testers said the Modibodi pair fit true to size, provided sufficient protection and, because of the style—a standard bikini with a subtle lace trim on the waist—look like something they’d pick out at a store whether they were period underwear or not.

The only caveat is the crotch area, which has noticeably thick padding—not quite as thick as a maxi pad, but thicker than a standard pair of underwear—that some people might find uncomfortable. Still, if you’re planning on wearing period underwear on heavy days or overnight, this Modibodi pair is your best bet.

Also, Modibodi ships out of Australia, so it can take a while to arrive—one order I placed took about two weeks, though another only took about a week.

The Modibodi Sensual High-Waist Bikini comes in women’s sizes XS to 6XL.

Pros

  • Comfortable

  • Stylish

  • Absorbent, holds a super-tampon's worth

Cons

  • Thick padding in the crotch area

  • Ships from Australia

Product image of Thinx Super Hiphugger
Thinx Super Hiphugger

The Thinx Super Hiphugger claims to hold up to four tampons’ worth of blood—and, as far as I could tell, this is accurate. This pair scored third in our lab tests, right behind both Modibodi pairs. And when I wore this pair, I felt securely leak-free. It also looks nice, with a full-coverage bottom and lace trim around the waist.

The main drawback of this pair is that the outer shell is made of a slick fabric that looks and feels like a bathing suit. There isn’t anything wrong with this, but I didn’t love the way it felt when it rubbed against my clothes.

The pair also has extra thick padding in the crotch, even thicker than the Modibodi pair. Though this undoubtedly helps them maintain the four-tampon claim—and does a good job of absorbing liquid quickly and resisting sogginess—wearing it felt a little more diaper-y than I would have liked, just because the lining was so hefty. Still, leaking was never a concern when I wore the pair overnight, so it’s a great option for nights or heavier days.

The Thinx Super Hiphugger comes in women’s sizes XXS to 3XL.

Pros

  • Holds up to four tampons' worth of blood

  • Full coverage

Cons

  • Feels a little like a diaper

Product image of Dear Kate Nellie Hipster Full
Dear Kate Nellie Hipster Full

The Dear Kates Nellie briefs, which claim to absorb up to two tampons’ worth of blood, placed fourth overall in our lab tests. They had the quickest absorption time of any we tested, soaking liquid up almost immediately in the crotch without dripping moisture through to the other side. They were easy to wash because the gusset is built into a wider area than most period panties, which means they have fewer seams (and fewer creases for menstrual fluid to get stuck in).

They also look pretty good, if not as stylish as the Thinx and Modibodi pairs—most testers were unimpressed, but not turned off by their aesthetics. “These were exactly fine in terms of looks,” one tester says. “They're not ugly, but they're more function than fashion.”

My main issue with them was the slippery material on the external shell of the underwear, which gave them a distinct look—and feel—from other pairs of underwear in my drawer, almost like wearing cheer briefs under my clothes. Also, this pair seemed true to size for me, but some testers complained theirs ran small, particularly around the legs.

Their absorption is great, though, so if that’s all you’re looking for, these briefs are worth a try.

Dear Kate Nellie Briefs come in women’s sizes XS to 3X.

Pros

  • Quick absorption time

  • Easy to wash

  • Holds two tampons' worth

Cons

  • Runs small around the legs

Product image of Modibodi Seamfree Bikini - Moderate / Heavy Absorbency
Modibodi Seamfree Bikini - Moderate / Heavy Absorbency

The Modibodi seamfree bikini came in second place in our lab tests, right behind the high-waist bikini in our tests. This is significant, as the seamfree bikini is listed as having “moderate-heavy” absorption compared to the high-waist bikini’s “heavy-overnight” absorption.

The fabric it’s made of is nice—a silky elastane that feels close to a regular seamfree pair I have from ASOS—but because it’s thin (a byproduct of being seamfree), the padding in the crotch really stands out. It’s not prominent enough to see through clothes, but you definitely notice it when it’s on, and I felt a little weird putting it on at the gym. That said, I found it effective during my period—except for one thing. The crotch area, though absorbent, often crinkled up when I sat down. Because of this, I had to unfold it every time I went to the bathroom to prevent spillage. No leaks happened, so it wasn’t disastrous, but it wasn’t ideal.

The Modibodi Seamfree Bikini comes in women’s sizes 2XS to XL.

Pros

  • Fabric feels nice

  • Absorbs a lot of liquid

Cons

  • Crotch area crinkles up when sitting

Product image of Saalt Elemental Bikini
Saalt Elemental Bikini

It’s common practice for period-havers to divide the underwear they own into at least two categories: Cute underwear, and underwear to wear when you’re on your period. Most absorbent period panties fall into the latter category—serviceable, but not exactly a pair you’d want to wear on an occasion when someone else could be seeing them. But the underwear from Saalt, a menstrual cup brand that recently branched into menstrual wear, is a rare exception. Saalt’s panties are made of a lightweight, silky material and have mesh or lace cutouts that make them look sleek and sophisticated. The absorbent gusset built into the crotch is also thinner than expected, so there’s almost no tell that it’s there at all, especially if you get a pair in a darker color. All in all, they’re comfortable, lightweight, and easy to forget you’re wearing period underwear.

On the downside: The pair we tested, the bikini, was advertised as having regular to high absorbency. But we found that it was not as absorbent as others in the same purported range and experienced a few leaks in lab tests, so it’s not a pair to wear alone on a moderate or heavy period day. I wore the pair on its own on a lighter day, which worked well, and expect it would work as a backup with a tampon or menstrual cup on heavier days—I wouldn’t expect to use these as a full-time free-bleeding solution, though. But if you want a pair of period underwear that doesn’t look like, well, period underwear, Saalt is your best bet.

Pros

  • Cuter than most period underwear

  • Lightweight and comfortable feel

Cons

  • Experienced some leaks during testing

Product image of Aisle Boxer Brief
Aisle Boxer Brief

Aisle’s boxer boasts the same four-tampon capacity as the bikini, with its absorbent gusset-pocket and additional absorbency booster. In our tests, it prevented liquid from leaking through the fabric and didn’t feel overly damp, even when worn for long periods of time on heavier days.

The extra coverage of the boxer cut—which fits snugly, like a men’s boxer brief—also provided more security, as the leg fabric made it feel less likely that the booster could slip out. This makes the boxer cut a dream for nighttime use, especially for people who tend to move around a lot in their sleep. That said, the boxer has a lot of fabric, which can make it feel uncomfortable and look noticeable—occasionally even “diaper-like,” in one tester’s words—under most items of clothing. For this reason, this is a pair of period underwear that we recommend wholeheartedly for mostly sedentary period pursuits—say, snoozing and snacking while watching TV—but not for more active days. In other words, if you don’t mind trading a lot of bulk for extra protection, Aisle’s boxer will serve you well.

The Aisle boxer comes in women’s sizes XXS to 5X.

Pros

  • Great at preventing leaks

Cons

  • Excess fabric can be uncomfortable

Product image of Thinx Thong
Thinx Thong

The Thinx thong is... fine. It only claims to hold about half a tampons’ worth of fluid, so I didn’t expect too much from it in regard to period protection, and it met my mediocre expectations. It scored in the bottom-middle of lab tests, with some leaking but a decent liquid absorption speed.

I found the thong comfortable and cute enough, but it was nothing special. One reviewer noted that the lace started to separate from the underwear on one side after a wash, so it may not be as durable as some other pairs of underwear. The thong should work for a light day or as backup with a tampon or menstrual cup, but you shouldn’t plan on using it for much more.

The Thinx thong comes in women’s sizes XXS to 3XL.

Pros

  • Comfortable

  • Cute design

Cons

  • Not great for long term use

Product image of Sustain Period Underwear
Sustain Period Underwear

Sustain Natural, a company that makes organic pads, tampons, and condoms, also makes period underwear. The underwear comes in one style, a black cotton bikini, which the brand says holds the equivalent of one tampon.

My experience with them wasn’t memorable. In fact, I forgot I'd tested them when I was putting this article together until the very last moment. I liked that they are made of cotton and don’t require a supplementary pad, which made them feel more breathable than some other pairs. On the other hand, they look and feel like a frumpy pair of cotton undies.

I wore them on a light day, which went fine. (I don’t remember any leaks, anyway.) In short, the Sustain underwear does pretty much exactly what it claims, but they don’t reach as high as some other brands and are by no means the best of the bunch.

Sustain Natural Period Panties come in women’s sizes XS to XL.

Pros

  • Breathable

Cons

  • Frumpy looking

Product image of Bambody Absorbent Hipster
Bambody Absorbent Hipster

Bambody period panties, sold on Amazon, have good ratings—129 reviews and an average of 4.3 stars—but we found them to be just OK. In tests, they took a while to absorb liquid and had some minor leakage. I found that they ran small, and noticed that the gusset doesn’t extend to the back of the underwear, which could cause leaks if the underwear shifts forward during the day.

On its Amazon page, the brand advises pairing with a tampon, pad, or menstrual cup for best results—so, if you get them, do that, I guess. As a plus, they’re less expensive than most other brands— $14.90 for a pair or $29.90 for a three-pack —so if you test them out, you don’t have to sink as much money into them as you would for a pair of Thinx.

Bambody underwear comes in women’s sizes S to XL.

Pros

  • Inexpensive

Cons

  • Runs small

  • Takes a while to absorb liquid

Product image of Knix Leakproof Bikini
Knix Leakproof Bikini

The Knix Leakproof Bikini scored second-lowest of our lab tests, beating out only the thong of the same brand. That seemed to check out during my own test, too—I tried wearing it on its own, then, about an hour in, I realized I needed tampon reinforcement.

That said, the underwear is comfy enough, so it’s something I can see wearing on light spotting days or in tandem with a tampon—but definitely not solo when I’m in the throes of my period.

The Knix Leakproof Bikini comes in women’s sizes S to XXL.

Pros

  • Comfortable

Cons

  • Not good for heavy days

Product image of Knix Leakproof Thong
Knix Leakproof Thong

The Knix thong does one thing really well: staying invisible under clothes. Other than that, it doesn’t offer much—it had the lowest score in our lab tests, due to noticeable leakage and just so-so absorption. Stains also seemed to stick to them more than other pairs.

Wearing the thong wasn’t the most rewarding experience, either. I found that it gave me too much of a wedgie feeling, even for a thong, and the padded area didn’t quite line up with the area that needed it, which, if I’d been wearing it on a heavy day of my period, wouldn’t have been ideal.

I might suggest wearing these on super light days, or maybe under leggings during a workout as tampon backup, but not for anything other than that.

The Knix thong comes in women’s sizes S to XXL.

Pros

  • Stays invisible under clothes

Cons

  • So-so absorption

  • Uncomfortable

Product image of Ruby Love Period Underwear Hipster
Ruby Love Period Underwear Hipster

The RubyLove Hipster didn’t fare terribly in lab tests, placing about fourth to last when compared to other brands. But in my practical test, it was a massive flop. The pair has a thick gusset, and RubyLove’s site claims the underwear provides “100 percent leak-proof protection,” so I thought they would be OK to wear on a medium-heavy day of my period. This was not the case! I wore the underwear out on a Saturday, and within two hours I had bled through it and onto my shorts, causing me to run into a Starbucks bathroom and create an emergency middle school-style toilet paper bundle.

The RubyLove pair also has a movable mesh layer on the crotch that can be used to hold reusable pads sold by the brand (though the pads aren’t supposed to be necessary for period protection). Not only does this feel weird if you don’t have one of the pads, but it also makes it so that anything that comes out during a period is really hard to wash out. I’m sure the underwear does work better with a pad and would be fine on its own on a light day, but I can’t recommend them based on my experience.

The RubyLove Hipster comes in women’s sizes XS to 3XL.

Pros

  • Can hold reusable pads

Cons

  • Doesn't absorb well

Meet the tester

Sara Hendricks

Sara Hendricks

Editor

@sarajhendricks

Sara Hendricks is an editor with Reviewed covering health and fitness.

See all of Sara Hendricks's reviews

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