Best (& Worst) Period Underwear & Period Panties Tested for Indications of PFAS

Period underwear or period panties are super absorbent and a lifesaver for women when their period has come, but some of them could also be coated with persistent & hormone-disrupting Per- and polyfluoroalkyl substances (PFAS) chemicals. The Mamavation community members asked us to start testing “leak-proof” period underwear to see if it had any traces of PFAS so we did. And we have continued to test for over two years. So which period underwear is less likely to be made with a PFAS coating and better for your active lifestyle? You’ve trusted Mamavation to bring you topics like best non-toxic cookware, best air purifiers for the home, & best organic mattresses, now join us for the best & worst non-toxic period underwear with lab results showing that 65% of products tested could be contaminated with PFAS. Scroll down to the bottom if you want to see the raw data.

Disclosure: This post was medically reviewed by Hannah Gardener, Epidemiologist at Agreenslate.com. This post also contains affiliate links. 

Period Underwear Could Be Exposing Consumers to Toxic PFAS

In early 2020, Jessian Choy, a journalist at Sierra Magazine (from the Sierra Club) shared results from the Laboratory of Applied Nuclear Physics at the University of Notre Dame regarding potential PFAS contamination in the most popular period underwear brand–Thinx.

We interviewed Jessian Choy and she told us that after years of wondering if this type of underwear contained a type of PFAS chemical, she decided to enlist the help of Dr. Graham Peaslee, a fellow at the American Chemical Society and professor of Applied Nuclear Physics. Dr. Graham Peaslee was also concerned with the potential outcome of PFAS in period underwear after releasing similar results about American food packaging. Peaslee has been researching PFAS for the past few years and was the scientist that discovered the presence of PFAS in fast-food wrappers in 2017. He’s also served as an ambassador for the newly debuted film starring Mark Ruffalo about PFAS called “Dark Waters,” in which he led a discussion about PFOA at Notre Dame University.

The results from these panties were shocking because they made it clear that products like period underwear could be manufactured with PFAS chemicals inside their “moisture-wicking” fabric and sold to unsuspecting American consumers. Since your period undies are right up against the vagina, it’s an important dermal exposure as it lies snug against the vulva for an extended period of time. Because scientists are already concerned about dermal exposure, it could be a very relevant avenue for toxic pollution into the body.

After Dr. Peaslee found fluorine in Thinx panties and it was covered by the Sierra Magazine, it was followed by Thinx denying any responsibility or possibility that it was true. Thinx then hired consultants (who were infamous for representing toxic chemical companies and thwarting regulation & public policy hard on toxic chemicals like perchlorate) to refute the findings of what Dr. Graham Peaslee found in his lab at the University of Notre Dame.

Shortly following the denial, Thinx changed the language on their website to allow them to sell Americans period panties with PFAS without getting into hot water. (We know because we checked.) Basically, any reference to the “PFAS” chemical category was removed, and instead, they replaced it with language that only claimed they were free from PFOA, which is one specific chemical within the class.

We also noticed other brands making similar changes in legal terms on their sites, but not all.

So in other words, the brands like Thinx haven’t changed their product, but they have changed the way they talk about their product. They aren’t telling you no PFAS chemical is present, they are instead telling you PFOA (one of the thousands of chemicals in that category) isn’t present. But obviously, there is more to worry about inside those panties than PFOA.

What about the other 12,000+ PFAS chemicals? Shouldn’t we know about those too? Mamavation reported on these findings in early 2020. Afterward, the community was very concerned about this product category and asked us to start testing different brands of period underwear to get a better understanding of which brands did not have any detectable fluorine. So this is exactly what we did starting in 2020 and you are reading the results of our privately commissioned study today. We have continuously added to this study with additional results as they are donated brand new in packaging to us by fans. 

Why PFAS Chemicals Are Problematic Around Your Vagina

PFAS chemicals, otherwise known as per- and polyfluoroalkyl substances (PFAS), have been dubbed “forever chemicals” because of their staying power. These chemicals are extremely problematic to human health and the environment because they are persistent, meaning they build up and don’t go away. They resist degradation in the environment and they remain in our bodies for YEARS after exposure, sometimes decades.

“The fact that this is a preventable exposure that accumulates in the body, and young child-bearing-age women are being exposed has impacts not only for those who use this underwear, but also potentially for their future children because these compounds stay in our bodies for years!” says Hannah Gardener, founding epidemiologist at Agreenslate.com and Advisor to Mamavation. “These underwear with ‘forever chemicals’ have environmental implications from production to being washed in our washing machines all the way to the end of their life cycle in landfills.”

Researchers are also very concerned about dermal contact of PFAS and are worried that the health outcomes may be similar to ingestion. Therefore, it’s important to avoid PFAS as much as possible around the vaginal area and any other area because it builds up in the body. 

In other words, they are not quickly excreted from our bodies like other hormone-disrupting environmental contaminants. And that staying power has become a very big deal in food packaging, water…and now fabrics.

I highly recommend watching Dark Waters, a true story about PFAS chemicals contaminating small-town America starring Mark Ruffalo, Anne Hathaway, and Tim Robbins. This short trailer will give you a quick understanding of what is happening around the United States to our water supply. And it’s quite serious.

Potential Health Effects of PFAS Chemicals from Research

PFAS (aka PFCs or perfluorinated chemicals, including PFOA and PFOS) are added to many products we purchase to make them “stain-resistant,” “grease-proof,” and “water-resistant.” In food packaging, they are used in popcorn bags, pizza boxes, fast food canisters & wrappers, and the flat dish on the bottom of cakes. They are also in carpeting, furniture, & clothing as “stain-proof” agents.  You can also find them on non-stick pans, some tooth flosses, and cosmetics.

Here is the list of health problems (PFAS) perfluorinated chemicals are linked with.

• Reduction in immunity
• Reduced vaccination response
• Increased risk of allergies & asthma in young children
• Affected growth, learning, and behavior of infants and older children
• Increase cholesterol levels
• Metabolic diseases like obesity & diabetes
• Cardiovascular disease
• Lowered a woman’s chance of getting pregnant
• Lowered male fertility
• Increased risk of kidney & testicular cancers
• Causes endocrine disruption
• Disrupted normal thyroid function

“These results add to the growing body of evidence reaffirming that we need to know more, not less, about the ingredients in period products. Millions use menstrual products monthly. It is unacceptable that there are so many unknowns about the ingredients, safety, and health impacts of products that come into contact with one of the most sensitive and absorbent parts of the body,” said Alexandra Scranton, Director of Science and Research at Women’s Voices for the Earth (WVE), a national environmental health organization, that has been advocating for ingredient transparency and safety of period care products for the last decade. “Furthermore this new testing also shows that PFAS-free period underwear is possible. Which means, not only are these chemicals adding potentially harmful exposure to our bodies and the environment, but they are also unnecessary to the performance and efficacy of these products.”

If you feel like you’ve been exposed to PFAS, the Agency for Toxic Substances and Disease Registry, a division of Community Health Investigations has created this fact sheet to use when talking to your doctor.

Why Are Brands Claiming They Are PFAS Free When They Are Not? Overstating OEKO-TEX® Certification Was One Issue.

We noticed that some brands were making claims of being PFAS-free because they use OEKO-TEX® certified fabrics and were under the impression that OEKO-TEX® means “PFAS-free.” We found this assumption NOT to be true. After discovering examples of OEKO-TEX® certified period panty fabrics testing for high levels of fluorine, Mamavation decided to investigate further.

We interviewed Ben Mead, Managing Director of Hohenstein Institute America, which is a company that manages the OEKO-TEX® standard in the United States. Ben made it clear to us in an interview over the phone that OEKO-TEX® tests for only 30+ the most common PFAS chemicals directly like PFOA and they do not test their fabrics for fluorine at all.

Because OEKO-TEX® does not test their approved chemicals for fluorine, we cannot be sure they do not contain any of the other thousands of PFAS chemicals they are not testing for. 

It’s like a “test no evil see no evil” type of situation.

OEKO-TEX® has added some additional “PFOA-like” chemicals to their testing in 2021, but we are still not convinced they are looking for every possible PFAS chemical, especially the “short-chain” ones. Therefore any brand that is relying on OEKO-TEX® to make that claim, may actually be in for a big surprise. Sadly, It’s not fool-proof as you’ll see in the results we got.

As we were interviewing brands about this topic, it was clear to us that most of them were not even aware you could test for fluorine as a way to spot “short-chain” PFAS chemicals in their panties.

The only industry excelling at testing for fluorine instead of each PFAS chemical individually is the composting & food packaging industry. Period underwear companies need to catch up.

Mamavation’s Scientific Advisor Pete Myers Explains Why Current Federal Testing Requirements Are Not Enough To Protect Families

Pete Myers, our main scientific advisor, gave us an interview about what the problems are in terms of how chemicals are evaluated at the Federal level and how that leaves HUGE gaps of concerns for families, particularly women & children.

Pete Myers reviewed three problems that exist that can be adjusted to make pregnant women and families safer. Most of the problems are around how the chemicals are tested and regulated.

Low Dose Testing of Chemicals Isn’t Required By Feds & It Should Be

You know that saying “dose equals the poison?” It’s the idea that chemicals are only dangerous at various doses inside your body. High doses may cause death so they are typically avoided, but what if low doses could also cause damage over time?

First, the Feds assumed that high dose testing will tell them everything they need to know about low dose testing without doing the low dose testing. According to Pete, they do the high dose testing and then extrapolate what they think will happen at low doses. However, nothing is actually done to look at these low doses.

While that works with some poisons according to Pete, it emphatically doesn’t for endocrine-disrupting compounds. And that’s because different genes get turned on and off at different parts of the dose-response curve. What happens at low doses can be just the opposite of what happens at high doses. And because of the way they structure their tests, they never dose at the low levels that are relevant to most people’s experience.

In other words, they really have no idea what will actually happen. They are guessing.

Pete has written multiple scientific (and peer-reviewed) papers on this. You can find two of them here and here. And when he published the second one the country’s top toxicologist, Dr. Linda Birnbaum, former director of the National Institute of Environmental Health Sciences wrote an editorial concluding that this should be the general expectation for endocrine-disrupting compounds.

Should low-dose testing be considered? I guess it depends on what your interpretation of “safe” is. If you don’t want to know, don’t test.  If you don’t test low doses, you definitely won’t understand their impacts.

Only the Active Ingredient is Analyzed to Determine Safety Leaving Out Real-World Exposures

Second according to Pete, when the Feds test pesticides, they only test the active ingredient. They aren’t looking at our real-world exposure of a complete formulation, just certain ingredients inside. And that is also completely absurd. It’s like testing the tomatoes in a spaghetti sauce but missing the oils, herbs, and other ingredients.

Refusing to test the entire formulation means they don’t know how it’s reacting with your body as it’s sold or applied. The actual product contains a complex mixture of other chemicals that are included specifically to make the active ingredient more toxic. And it’s not just pesticides that have this problem. We live in a soup of nasties that can interact in ways that dramatically make the mixture more dangerous than just one chemical. Is this toxic soup safe? I guess it depends on what your interpretation of “safe” is.  If you don’t want to know, don’t test the products the way families experience them in their homes.

The Feds Use Antiquated Testing Instead of Modern Testing to Evaluate Modern Chemicals

Third according to Pete, the tests they use are way out of date. The Feds rely on antiquated testing compared to the tools that independent scientists use when examining toxicity.

Here’s Pete’s analogy–”Imagine you’re an FDA employee and you’ve just seen photographs in National Geographic of distant galaxies taken by the Hubble Space Telescope. You’ve never seen anything like it. So what do you do? You grab your binoculars and go into your backyard at night, look up toward the stars, and see nothing like those photographs. You don’t see anything so you conclude the photographs are FAKE NEWS.

One of the crude tests the EPA and FDA use was actually developed in the 1930s. In case they didn’t know, medical science has advanced a lot since 1935. Their tests are totally insensitive to what we need to know about endocrine-disrupting chemicals. To determine what is “safe” you need to use modern medical tools. Not surprisingly, they aren’t finding anything, so they are able to say “no danger here!” But does that mean they are right? I guess this depends on what your interpretation of “safe” is.

Mamavation’s Investigation of Period Panties & Period Underwear

Mamavation tested the most popular period panties (some up to 4x) looking for fluorine, the chemical that unites all PFAS chemicals. This is important to understand–because there are thousands of PFAS chemicals in commerce and most are not even possible to find because we do not have the tests available, we are testing for fluorine instead. This is exactly what the food packaging industry does to determine whether PFAS was “intentionally added” and can be composted or not. So this standard already exists in other industries and within different state laws formulated around packaging and PFAS and can be a valuable tool to period underwear companies when testing their own products for PFAS.

Because testing for fluorine is the only standard that is out there, we’ve adapted this to fabrics and are using it for this investigation on period underwear. BPI Industries uses the standard of 100 ppm of fluorine to determine if PFAS was intentionally added, so we’ve done the same.

Brands with over 100 ppm of fluorine go into the “not our favorite” category, while brands that test between 0-100 ppm will be in the “better” category, and brands that don’t have any fluorine residue will be in the “best” category.

Results From Mamavation’s Study on Period Panties

[UPDATED WITH ADDITIONAL PRODUCT SINCE ORIGINAL STUDY POSTED. Mamavation has accepted donations of brand new period underwear products and has continued to update this recommended list. August 16, 2021: Mamavation added additional results from 2 period underwear brands bringing the total up to 19 period underwear products tested. UPDATED October 15th, 2021: Mamavation added 1 additional brand bringing total to 20 brands. Those new brands are marked with a *. UPDATED June 15th, 2022 Mamavation added 1 additional brand bringing the total to 21. UPDATED June 23rd, 2022 Mamavation added additional brands.]

ORIGINAL STUDY MAY 24, 2021: Mamavation sent 17 pairs of period underwear from 14 brands to an EPA-certified laboratory that used the determination of total fluorine by oxygen flask combustion and ion-selective electrode analysis. The level of qualification (LOQ) was 10 parts per million. We did not test panty liners, tampons, menstrual cups, period swimwear or regular underwear. We tested a bikini, briefs, waist bikini, high-waist, boxer briefs, & super hiphugger period underwear advertised to accommodate heavier flow days in sizes from XS to XXL. Here are the major findings from our laboratory:

• About 65% of the products tested had detectable levels of fluorine present in either the outer or inner layer of the crotch. Of the 17 pairs of period underwear tested, 11 pairs had detectable fluorine present.
• 35% of the products tested did NOT have detectable levels of fluorine present in either the outer or inner layer of the crotch. Of the 17 pairs of period underwear tested, 6 products did not contain detectable levels of fluorine.
• 57% of period underwear brands tested had detectable levels of fluorine present in either the outer or inner layer of the crotch.  Of the 14 period underwear brands tested, 8 brands had detectable levels of fluorine present.
• 3 brands of period underwear had levels of fluorine over 100 ppm, with one as high as 940 ppm.
• 2 brands of period underwear had products with various levels of fluorine detected so they are found in different levels of the investigation.
• 7 brands of period underwear had products with lower levels of fluorine present suggesting they may have been exposed unintentionally from processing or from the packaging.
• 6 brands of period underwear out of 14 brands were completely free of detectable fluorine, suggesting PFAS chemicals are not needed in period underwear at all. (Today that number is higher!)

Not Our Favorite Period Underwear Brands

These brands tested at over 100 ppm of fluorine. We tested several types of brands and retested different types of underwear for some brands that ended up here. The 100ppm standard is the same standard used to determine if food packaging is compostable. It’s not a perfect standard, but this is what we have. However, we make no claims as to how much fluorine is dangerous vs. safe for dermal exposure in your vaginal area. We simply do not know.

• Thinx Bayshort–619 ppm fluorine
• Thinx High Waist–940 ppm fluorine
• Thinx BTWN–132 ppm fluorine
• Knix High Rise–373 ppm fluorine
• Proof Hipster–234 ppm fluorine

Better Period Underwear Brands

Fluorine was found but under 100 ppm. That specific level is the same standard to determine whether food packaging is compostable, so we are using it here for similar purposes. However, we make no claims as to how much fluorine is dangerous vs. safe. We simply do not know.

• Cora–14ppm & 13ppm organic fluorine* (new brand added)
• Knix Boyshorts–43 ppm fluorine
• Knix High Waisted Period Underwear–17 ppm fluorine (new results added)
• Joyja–18 ppm fluorine
• Maxim Hygiene–26 ppm organic fluorine (new brand added)
• Panty’s— 37 ppm organic fluorine (new brand added)
• RAEL Period Underwear— 15 ppm organic fluorine & 10 ppm organic fluorine (Update: 4/27/23)
• Red Ruby Box–27 ppm & 22 ppm fluorine
• Sustain Natural–71 ppm & 17 ppm fluorine
• Thinx Speak High Waist–10 ppm fluorine
• Victoria’s Secret–20 ppm & 12 ppm fluorine

Best Period Underwear Brands

Mamavation used an EPA-certified lab to do this testing. No fluorine was detected in any of these products sent to the lab in 2020 and 2021. The Level of Qualification (LOQ) for testing was 10 parts per million, therefore if products had fluorine at lower levels, the test would not find it. We cannot guarantee these brands will continue to test the same. This was only a snapshot in time to help guide you in purchases. Most brands are using a thin layer of polyester or nylon to capture up to 5 tampons’ worth of heavy flow and keep it in your panties.

• Lilova (no fluorine detected)(*newest brand added) Use discount code “MAMAVATION15” for 15% off your order. 
• Aisle (formerly known as Lunapads) (no fluorine detected) Use discount code “MAMAVATION_10” for $10 off any order over $35 placed on periodaisle.com here.
• Bambody (no fluorine detected testing in 2021)(additional testing in 2023 was non-detect for organic fluorine)
• Innersy Big Girls Period Underwear — non-detect organic fluorine testing update 6-23-23
• Intimate Portal (no fluorine detected)
• June Period Underwear (no organic fluorine detected) (Updated: 4/27/23)
• Period (no fluorine detected) Use discount code “MAMA” for a special sale of “Buy 3 panties and get 1 free”
• Modibodi (no fluorine detected) Use discount code “MAMA10” for 10% off orders over $100 for new customers. Not to be used in conjunction with any other offer, on sale, gift cards or bundle packs. Limit one per customer.
• Revol (no fluorine detected) Use discount code “MAMAVATION” for 15% off your first purchase.
• Saalt Period Underwear— non-detect organic fluorine result 2023. (Prior testing in 2021 had a detection of 10 ppm fluorine. Kudos to Saalt for fixing this issue!) Use discount code “MAMAVATION” for 15 % off your first purchase. One use per customer, excluding bundles.

Conclusion of Mamavation’s Period Underwear Investigation

Mamavation hopes that this investigation will be useful in giving consumers an idea of what is inside period underwear and give regulators a clearer picture of what is happening in this industry right now. We also hope this investigation will be used by regulatory bodies to ascertain the potential risks to anyone wearing period underwear.

This investigation was independently funded by Mamavation. We also wanted to remind you that above you will find affiliate links that will be used to reimburse our costs. If you have found this investigation useful, we encourage you to browse the site to find other investigations like cookware, organic mattresses, air purifiers, or probiotics to name some of our most popular.

And if you would like to join our supportive community for women, where you can have some say in what products we look into, you can click to apply here.