The Best Period Underwear, Following Months Of Testing

The menstrual market has long just included two choices—pads and tampons. But thankfully for the nearly 2 billion people worldwide who menstruate every month, period underwear provides another appealing option. Designed to absorb a large amount of liquid, this breathable, sleek underwear offers a sustainable (and often easier to wear) alternative. After testing seven different brands, I determined the best period underwear for heavy flow to be the Aerie Real Period Boybrief Underwear. For low to moderate flow days, I recommend the Knix Leakproof High Rise Bikini Bottom.

The following is a list of all the winners from my testing process:

Over the course of two menstrual cycles, I wore all seven options at least once, observing how each pair absorbed menstrual liquid and held up to multiple washings. To gain more insight into what to prioritize in a pair of period underwear, I consulted two experts, Dr. Stephanie Hack, MD/MPH, OB-GYN and Dr. Jon Chorover, head of the Department of Environmental Science at the University of Arizona. Read on for my recommendations for the best period underwear and to learn how I conducted my thorough evaluation with each pair.

The Aerie Real Period Boybrief Underwear won as the top option overall because it’s highly absorbent, comfortable and leak-free. I wore this pair on day 2 (my heaviest day) and day 5 during my first cycle. During my second cycle, I wore them on day 2 again and put them through their paces with a workout and an active day chasing my children around. I never experienced a leak, and I got about 6 hours out of them before I felt like they had stopped absorbing moisture, which is about three tampons’ worth of fluid (even more absorbency than the two tampons’ worth advertised).

Aerie’s boybriefs look large out of the package, and the gusset (or crotch) is noticeably thick. But these briefs weren’t obvious under my clothing, and I stopped noticing their bulk very quickly. Compared to many of the other underwear I tested, the Boybriefs are a more attractive option and did not give off grandma vibes. The brand recommends hand-washing with cold water the first time, likely to set the colors, and putting the briefs in a mesh laundry bag in the dryer. After that, you can wash this underwear with other items, and even after four washes, I found the Boybriefs held up amazingly well. (You can read about my in-depth experience with these underwear in my full review.)

American Eagle (Aerie’s parent company) also confirmed plans to eliminate all Polyfluorinated Substances (PFAS) by 2024, noting in early 2022 that none of their products will contain PFAS after that point; still, compared to other brands, I found Aerie to be a bit less transparent about lab testing for PFAS (more on this below).

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Knix period underwear is stylish, ultra-soft and reliable on light to moderate flow days. The Leakproof High Rise is made with nylon and Lycra, with a cotton and spandex gusset, and is not meant to absorb more than 3 teaspoons of liquid. To test that limit, I wore these on a travel day while my period was moderately heavy, not light. About 3 hours in, I started to experience leaks from the front of the gusset, which indicated that the absorbency had maxed out at around one tampon’s worth of fluid. Given this, I’d recommend using Knix during the lighter days of your period or only as a backup (with a tampon) on heavy days.

Still, they’re stylish, comfortable and offer decent protection when timed right. Plus, they don’t give you underwear lines and don’t feel like a diaper, which sets them apart from nearly every other type of period underwear I tried. As I mentioned in my full review of this underwear, Knix is also transparent about its PFAS test results; the brand has been sharing test results since 2020, and all of its products are certified PFAS-free. Like the Aerie underwear, Knix undies can be machine-washed, but you’ll need to wash them on cold and lay them flat to dry.

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If you’re looking for a budget pair of menstrual underwear, consider the Innersy Women’s Leak-Proof Period Panties Mid-Waist. These cotton briefs come in a three-pack and are best on low flow days to protect from spotting and leakage. You can also wear these as a backup option with a tampon. At $22, they’re a solid option for the price.

The Innersy underwear fits true-to-size, if a tiny bit small, and they come in the widest range of sizes of any underwear I tried. That said, the fabric isn’t the most absorbent; while the material in the gusset soaks up liquid, you won’t be able to wear them for more than 3 hours if you’re experiencing light flow. Cotton also tends to collect odors faster than other fabrics. I noticed a bit of pilling after three washes (they’re machine washable), so this pair likely won’t last for as long as the other underwear I tried. The brand provides no information about PFAS, which is common in budget underwear but might raise concern for some wearers.

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The Saalt Leakproof Comfort Brief earns high marks for its excellent absorbency, comfortable fit and chemical-free assurances. The material—a proprietary Tencel Modal made from renewable beechwood—is soft. Unlike some of the other underwear I tried, this pair didn’t chafe or cut into my thighs or waist. The brief style is lower-cut than others, but it fits true-to-size. During my cycle, I wore these on my heaviest day, while working at my office, and I didn’t experience any leakage after 7 hours. And there’s another perk: If you’re worried about the PFAS that have been found in some super-absorbent products, you can feel safe knowing that Saalt’s labs provide testing details that guarantee these undies are PFAS-free.

Saalt’s Comfort Briefs come in slightly more limited sizes than some of the other options I tried. And beware that they’re also very thick—like a diaper—and they felt visible when I was wearing tighter pants. You’ll need to machine-wash them on the cold setting and then hang to dry. The Saalt briefs are not quite as durable as the Aerie and Knix options; they started to look a little pilled after three washes. But if you’re intrigued by the mid-rise fit, the soft fabric and their ability to tolerate the heaviest flows—and you’re willing to pay nearly $40 per pair—I definitely recommend the Comfort Briefs.

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Other Period Underwear I Tested

I tested three other products while determining the best period underwear. Though these were outperformed by my four winners, they might still fit your specific needs if the above options don’t work for you.

Bambody High Waist Period Underwear (OOS): These are made of eco-friendly materials (mostly bamboo, with some cotton and spandex in the mix). The high-waisted fit feels supportive, and I didn’t experience any chafing. But the absorbency leaves much to be desired: After 3 hours on a moderate flow day, I found that these felt full and smelled musty. They didn’t leak, but I wouldn’t be confident wearing them all day.

Proof Leakproof Hipster Underwear: The Proof undies are itchy, with a diaper-like feeling around the seat and fabric that uncomfortably snagged against my skin and caused a rash. I wore these on day 2 and day 4, and while they contained liquid just fine for a few hours, they started to smell musty several hours in. (The brand says they can hold five regular tampons’ worth of fluid, which I didn’t find to be true.)

Ecowoman Classic Period Panties: I wanted to like these eco-friendly period underwear, which come in sizes XS to 4XL and are made from bamboo fiber (with polyester and nylon in the lining). But they’re unflattering, uncomfortable and look (and feel) like a diaper. The waistband and leg holes cut into my skin, and they feel more itchy than most of the other options I tested.

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How I Tested The Best Period Underwear

For this guide, I conducted extensive research to narrow down the best options. After comparing more than 20 pairs of underwear across multiple brands, I opted to focus my testing on classic cuts that ranged from light to heavy absorbency and those for overnight use.

Safety

I spent a fair bit of time researching the 2023 class action lawsuit against Thinx, a brand which I decided not to test out. In short, some pairs of Thinx underwear (and underwear from other major brands) were found to include per- and polyfluroalkyl substances (PFAS), which are human-made chemicals that have been linked to adverse human health effects. Thinx settled the suit, and the brand still denies that PFAS have been found in its products. While you should be able to continue using Thinx, given the brand’s newly heightened testing protocols, I did not include them in my testing lineup out of an abundance of caution.

Use During Cycle

Next, I ordered seven pairs of period underwear and wore them each at least once during two of my cycles. I used each during the times in my cycle that they were specifically targeted for. (For example, I wore the Innersy Women’s Leak-Proof Period Panties Mid-Waist on the first day of one cycle when I wasn’t expecting much fluid, but I tried the Proof Leakproof Hipster Underwear on the second day, when my cycle tends to be heaviest.)

Durability

The final step of my testing was around the durability of the products. Period underwear is appealing to many for its sustainability: You can wash and reuse them instead of throwing out a tampon or pad. To be truly sustainable, the product should maintain its effectiveness and comfort after dozens of washes over a period of at least 6 months. For the purposes of this review, I washed each pair a minimum of four times, following care instructions. I never left damp period underwear sitting in the hamper. Instead, I rinsed them before washing, put them in the washing machine and let them line dry.

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