Do your period panties contain toxic chemicals called per- and polyfluoroalkyl substances (PFAS)? Last week, Jessian Choy from the Sierra Club posted about how she sent Thinx underwear to a lab that frequently tests for PFAS to see if her menstrual underwear was problematic to public health. The results and aftermath were shocking, but Mamavation is going to break all this down for you to so you don’t fall for any more marketing spin. You’ve trusted Mamavation to bring you topics like best & worst organic mattresses, best & worst makeup, & best & worst cookware, now join us for an explosive story about the period panties we’ve all grown to love.

Disclosure: This post was fact-checked by Hannah Gardener, Epidemiologist at A Green Slate. This post also contains affiliate links. The pictures displayed are Thinx panties from Leah Segedie’s personal drawer. She was sent Thinx underwear in 2019 for consideration of a review and wore them only once. They were not comfortable so they were not worn again, but she cut them apart and took pictures for the purposes of showing what the inner liner looked like.

Jessian Choy Had a Hunch About PFAS & She Was Right

Jessian Choy had been wearing Thinx menstrual underwear since 2016 and had a sneaking suspicion that it wasn’t as magical as it was marketed to the public. So she purchased several extra new pairs of menstrual underwear from the website and sent them directly to the University of Notre Dame to investigate. In other words, she never handled the product herself and sent them directly to the lab. After a couple of months, Dr. Peaslee returned with some very serious results–Her Thinx menstrual panties that she sent them were contaminated with PFAS, a very toxic hormone-disrupting chemical. The same brand she had been wearing for about 3 years could be disrupting her hormonal health. It WAS too good to be true.

She sent the lab at Notre Dame two different brands–Thinx and Lunapads. Dr. Graham Peaslee, a fellow at the American Chemical Society and professor of Applied Nuclear Physics, volunteered to test her panties for toxic chemicals. 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 newly debuted film staring Mark Ruffalo about PFAS called “Dark Waters,” in which he led a discussion about PFOA at Notre Dame University.

The Results of the Notre Dame’s PFAS Tests From Dr. Graham Peaslee

Jessian Choy shared with us the original laboratory results she got from Dr. Graham Peaslee at the University of Notre Dame, so we could verify this is, in fact, true. We sent a request to Dr. Graham Peaselee asking for permission to share the raw data from that report. If he grants us permission, we will make sure to share it here. But until then, we wanted to give you the most pressuring results from the study.

• Thinx “organic” hip hugger briefs had 3,267ppm (parts per million) fluorine (a marker for the presence of PFAS) in the inside crotch area.
• Thinx Shorty BTWN-brand briefs had 2,053ppm (parts per million) of fluorine (a marker for the presence of PFAS) in the inside crotch area.
• Lunapads, on the other hand, was completely free of PFAS at the lowest detectable levels

Why PFAS Is Problematic to Human Health & The Environment

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 like Stainmaster carpets, Gortex and Scotchguard.  You can also find them on non-stick pans, some tooth flosses, and cosmetics.

But these chemicals are extremely problematic to human health and the environment. And the worst part is 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. In other words, they are not quickly excreted from our bodies like other hormone-disrupting environmental contaminants.

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

• low sperm count
• smaller penis size
• reduction in immunity
• metabolic diseases like obesity & diabetes
• reduced vaccination response
• affect the growth, learning, and behavior of infants and older children
• lower a woman’s chance of getting pregnant
• interfere with the body’s natural hormones
• increase cholesterol levels
• increase the risk of cancer like testicular, prostate and breast cancers

Based on the persistence of this chemical inside the body, it’s incredibly dangerous to be exposed throughout a lifetime because it will continue to build up. Therefore, it’s important to avoid these chemicals as much as possible. Avoiding PFAS inside your menstrual panties would be beneficial for your health.

Thinx Response to Claims of PFAS in Their Product Wasn’t Exactly Truthful Or Necessarily “Healthy” At All

Thinx swiftly responded to claims by Jessian Choy that her underwear tested positive for PFAS with denials and claims of certifications. However, we looked into their claims and found some really big problems with what they were saying.

Maria Molland, CEO of Thinx stated: “Our customers’ health and safety is our number one priority, and we will always work to deliver the safest products available.”

They went on to make the following claims:

Claim #1: “All our Organic Cotton undies are OCS and GOTS-certified, which means even the farms we buy our cotton from are meeting organic certification standards, and our supply chain is carefully monitored to make sure the integrity of our cotton products never changes.”
Mamavation Investigates: We found the GOTS and OCS certification they were referring to, but they did not belong to Thinx. Instead, they belonged to a supplier, “Ocean Lanka.”  GOTS & OSC certifies a supplier of raw materials only. Thinx does not have its final product certified. We checked. They are simply holding up someone else’s certification and passing it off as their own. This means they are not bound by the standards of GOTS when producing this underwear at all. But they can say it’s “made with organic cotton.”

In fact, according to GOTS licensing agreement in section 4.4 it’s clearly stated: “in order that there is no misrepresentation that a product is GOTS certified, the GOTS labeling conditions do not permit the use of GOTS logo or any reference to GOTS (certification) on final textile products if the GOTS certification is valid only for immediate stages (such as yarn or fabric stage) for the specific components of the product only.”

Claim #3: “Our chemical testing is also done through a third party to ensure it’s honest and objective, and we’re proud of the fact that this testing has never detected any harmful chemical levels in Thinx underwear.”

Mamavation Investigates: We called and emailed Thinx and asked them specific questions about their testing and how it’s done. We heard back from them asking for a delay in posting this article several days later. However, they did send us exactly what we reported about above in their statement. So let’s take you through their own testing. After the first glance, it was evident that the laboratory was only testing for some PFAS chemicals and not any others. Here are the PFAS chemicals they were testing for.

• PFOA, Perfluorooctanoic acid
• PFNA, Perfluorononanoic acid
• PFDA, Perfluorodecanoic acid
• PFHxS, Perfluorohexane-1- sulphonic acid and its salts
• APFO, Ammonium perfluorooctanoate
• Henicosafluoroundecanoic acid
• TFDA, Tricosafluorododecanoic acid
• PFUnDA, Heptacosafluorotetradecanoic acid
• PFTrDA, Pentacosafluorotridecanoic acid
• GenX, 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propionic acid, it’s salts and its acyl halides (covering any of their individual isomers and combinations thereof)

Although this is quite impressive for PFAS testing, it’s not enough to make a statement that there are no PFAS chemicals present in the product. There are many other PFAS chemicals inside the chemical category, which has about 4,700 chemicals total in the PFAS family. In order to put this to rest the presence of fluorine would need to be testing, instead of looking at each chemical one by one. But it’s important to understand that all chemicals in the PFAS category (regardless if they are long-chain or short-chain) have these things in common:

1. They’re all man-made.
2. They contain linked chains of carbon and fluorine.
3. They are extremely persistent in the environment making them “forever chemicals.”

Testing for PFAS chemicals is complicated and if you don’t utilize the most sensitive of testing, you’ll miss most of them.

When you look at what Thinx says inside their FAQ (frequently asked questions) page and look into the claims, it’s evident that the inner layer or gusset inside the panties has been treated with some sort of unknown chemical that is not disclosed.

Claim #4: “The only treatments we use on the fabric of the gusset are moisture-wicking and anti-odor, which are both OEKO-TEX certified. We consistently test for all known regulated restricted substance for textiles.”

Mamavation Investigates: Again, OEKO-TEX 100 standard allows a myriad of  chemicals allowable for treatments. We found lots of “fire retardant” chemicals and “chemicals with biological activity” acceptable to OEKO-TEX. So technically you can’t say they avoid all PFAS chemicals. Even in their own standard, they restrict certain (not all) PFAS chemicals but do not ban them completely.

Claim #5: How Does Thinx battle odor? “The wicking layer of our signature period-absorbing technology has an application of non-migratory silver, commonly used in performance wear and medical devices to control odor and the spread of bacteria. “Non-migratory” means it won’t come off your undies and that it only responds to bacteria *on the fabric*, not on your skin (so your vaginal microbiome stays fresh and balanced!).”

Mamavation Investigates: In our research, we found that the use of nano-silver on clothing is mostly marketing in terms of preventing odor. But what we did find lots of information about nano-silver added to period panties being concerning when it came to vaginal health. Women’s Voices for the Earth produced a report in 2019 to explain.

• Silver can have an adverse impact on beneficial vaginal bacteria
• Nanosilver can also be cytotoxic, particularly to vaginal epithelial cells.
• Migration of nanosilver from period products into vaginal tissue and mucosa has never been studied.
• Silver-treated athletic clothing has been implicated in several cases of thermal burns when worn during an MRI treatment.

What’s Inside Thinx Period Panties?

Thinx discloses what each period panty material is made of minus the chemicals used to treat the inner gusset. You can find this information in the FAQ under the question “I have sensitive skin. What is Thinx made of? Will it irritate me?”

• For Thinx Classic — Gusset: innermost layer is 95% Cotton, 5% Elastane; Middle layer is 95% Cotton, 5% Elastane, and the outermost layer is Breathable PUL (poly jersey).  Body: Outermost layer is 85% Nylon, 15% Spandex and the innermost liner is 95% Organic Cotton, 5% Elastane.
• For Thinx Air — Gusset: innermost layer is 95% Cotton, 5% Elastane; Middle layer is 95% Cotton, 5% Elastane, and the outermost layer is Breathable PUL (poly jersey). Body is 78% Polyamide, 22% Elastane.
• For Thinx Super — Gusset: 100% Polyester and the outermost layer is Breathable PUL (poly jersey). Body: 95% Organic Cotton, 5% Elastane.

Polyurethane Laminate (PUL) VS. PFAS Treated Fabric

When it comes to polyurethane laminate (PUL) versus PFAS treated fabric, PFAS chemicals are far worse. We visited page after page of period panty sites and lots of them brag about not having PUL or using any plastics, but that’s a misleading health claim. When it comes to chemicals of concern, polyurethane laminate (PUL) is far less problematic to hormones and the environment than PFAS chemicals. We recommend you look for brands that use PUL.

Mamavation’s Investigation of Most Period Panties

Because we got our hands-on laboratory results of two brands: Thinx & Luna, we figured it may be good for us to go over some of these other popular brands to take you through their materials. Based on what was said on their websites, we are making some judgment calls. It’s very possible we could be wrong about some of these and we are still in the process of getting more information, but we will adjust this post as needed for future reference.

Brands We’d Prefer You Not Purchase

These brands either tested positive for PFAS, contain no “plastic” or don’t look to be careful about toxic chemicals at all.

• Amore/Ruby Love: This company avoids “Plastic, Polyurethane Laminate (PUL), plastic” but do not state what chemicals are used to treat fabric to make it leak proof. This leads us to believe they may be chemically treating the fabric with PFAS. (Update: This brand has responded they do not use PFAS chemicals and we have asked for them to disclose what chemicals they are using AND for laboratory testing results of several parts of the panties looking for the presence of fluorine. Will update this if and when they send that information.)
• Anigan: We are uncomfortable with their use of “fluid-resistant” & “moisture-resistant” fabric on the inside.
• Bambody Leak Proof: This company only sells on Amazon and doesn’t give us a clear picture of what is inside.
• Dear Kate: This brand brags having “three layers of breathable fabric make our undies leak resistant, stain releasing and moisture-wicking (NO plastic or films)” but unfortunately as you can see some plastic would do them some good here. We do not have proof their panties are PFAS treated but suspect they are.
• EvaWear: This company says they use “breathable panty is made of a moisture-wicking, highly-absorbent fabric” with no mention of PUL
• Hairbrained Design: Panties are 95% cotton & 5% elastane. Made in China.
• Knix Thong Panties: This company doesn’t explain what they do to create a period-proof panty at all.
• Mondibodi: Does not contain enough information about the technology used inside their product for us to tell how it’s treated or what it contains.
• PantiePads: This brand does not really explain what the contents of the panties are in general.
• Stelpa Period Panties: This company only sells on Amazon and other than saying they are “chemical-free and sustainable” we have no idea what they contain.
• Thinx Period Underwear: This entire post was dedicated to the laboratory results of this brand. We recommend you avoid them.

Better Brands But Without Testing We’re Not 100% Sure About Them

• Intimate Portal Panties: made with cotton and uses PUL for a lining
• Rael Organic Panties: made with organic cotton, but designed to be worn with a pad, liner, or tampon, so not considered true menstrual underwear.
• Sustain Natural Panties: made with organic cotton and uses a PUL for a lining

Best Brand We Can Recommend

• Luna Pads Maia Panties: Tested negative for PFAS chemicals. Has a polyurethane laminate topped with 100% organic cotton.

Want to know more about the best & worst menstrual products such as tampons, pads & silicone cups check out our feminine needs investigation.

Tips On How to Avoid PFAS In Your Home

The perfluorinated chemical category is all about making things grease-proof, water-proof and stain-proof. So think about stain-proof clothing & carpeting, nonstick pans & bakeware, fast food wrappers, contaminated water, etc. And here is a list of what you can do today to start avoiding these chemicals in your life.

• Phase-out the nonstick cookware in your kitchen. Here are the best alternatives.
• Make sure your tooth floss doesn’t have PFAS. Here are the best brands.
• Avoid foods with packaging and make things from scratch as much as you can from home
• If you purchase disposable plates, make sure to purchase the ones without PFAS. Here’s are those selections. 
• Avoid fast food as much as possible, even the ones touting themselves as “better.” Some wrappers and cane sugar fiber bowls like the ones at Chipotle contain PFAS chemicals to repel grease & water.
• Purchase a reverse osmosis water system for your home, especially if you live close to a military base or airport.
• When purchasing furniture or carpet, decline optional treatments for stain and dirt resistance. This is where you can find safer furniture. New good news: Home Depot phases our PFAS in Carpeting & Rugs
• Avoid buying clothing that bears a label indicating it’s water, stain or dirt repellant
• Avoid buying personal care products with the phrase “fluoro” or “perfluoro” on the ingredient list. You’ll find this inside lotion, pressed powders, nail polish, dental floss, and shaving cream.
• Dust more!  PFAS chemicals stick to dust particles so the more dust you have in your home, the more likely you will have PFAS in the air you breathe. Click here for our FREE eBook on how to clean your indoor air. 
• PFAS in Grocery Stores–Food Packaging (plates, bowls, take-out, etc)