Is Period Underwear Safe? The Answers Are Still Murky

As if periods aren't awful enough on their own, we have news that might make them worse — especially if you've come to love period underwear. A recently settled lawsuit claims that Thinx misrepresented its products as safe, sustainable, and free from harmful chemicals and nanoparticles. According to the lawsuit, third-party testing found that its menstruation underwear contains migratory nanoparticles and per- and polyfluoroalkyl substances (or PFAS), harmful chemicals that the CDC says are linked to fertility issues, environmental pollution, and certain cancers.

Thinx has agreed to put $5 million into a common fund to pay affected customers, and people who purchased Thinx underwear between Nov. 12, 2016, and Nov. 28, 2022, can go to the official settlement website to submit claims for compensation. You can receive a $7 refund for each pair of underwear purchased, with a limit of three pairs. (Most of Thinx's period products cost roughly $30 apiece.)

Even so, the company denies the allegations against its product, insisting the company did nothing "improper or unlawful" and that PFAS "are not intentionally added to Thinx Period Underwear at any stage of production."

People who've come to love Thinx products have been sharing their reactions to the settlement on social media. "I am very bummed about the lawsuits with Morphe, those organic tampons, and Thinx lately. Oh how I love being a woman," wrote one user. "[D]id people really think that ANY fabric would absorb your period blood and not create any odors —- wouldn't have insane chemicals in it???" tweeted another.

None of this necessarily mean you're in danger if you've used these products. The relatively short amount of exposure (i.e. during your period) shouldn't cause too much harm long-term, says Kelly Johnson-Arbor, MD, FACEP, FUHM, FACMT, medical toxicologist and medical director at National Capital Poison Center. But still, the idea of nanoparticles and PFAS near one's underwear is unsettling, to say the least.

POPSUGAR spoke to experts to better understand the risks associated with these substances, whether or not you need to worry, and what to keep in mind when making your next period-product purchase.

Editor's note: This information in this article is not medical advice and is for informational purposes only. You should always consult your doctor regarding matters pertaining to your health.

The Basics of the Thinx Settlement

The lawsuit alleges that Thinx was misrepresenting its products as a "safe, healthy and sustainable choice for women, and that it is free of harmful chemicals," when independent researchers found "forever chemicals" and migratory nanoparticles in its products, according to Class Action.

As part of the settlement, Thinx will pay up to $5 million to cover claims, maintain production controls, and conduct material reviews to ensure PFAS are not "intentionally added." This includes its raw-material suppliers, which will sign a "Supplier Code of Conduct and Chemical Supplier Agreement" that confirms that PFAS aren't used in production.

Also, Thinx can no longer refer to the antimicrobial components (used in Agion, the "odor-controlling technology") as "non-migratory." The lawsuit alleges that the silver and copper nanoparticles in Agion are so small that they are migratory and can "readily enter the human body through inhalation, ingestion, and skin absorption," according to Class Action. It furthers that "every published study of clothing containing nanosilver" has shown that the silver migrates and can be released into the human body or environment.

Thinx has denied all of the allegations made in the lawsuit and continue to confirm that PFAS have never been a part of its intentional product design.

What Are PFAS, and Are They Harmful?

Per- and polyfluoroalkyl substances, known as PFAS, are chemicals already found in many consumer products, including clothing. PFAS are a type of "forever chemical," a man-made compound that's utilized in everyday products to create nonstick, waterproof, and greaseproof characteristics, Dr. Johnson-Arbor says. They're been widely used in industry and consumer products since the 1940s, according to the CDC, and you can be exposed through drinking water, food, cleaning products, and personal-care products such as shampoo, dental floss, or makeup.

"These chemicals are called 'forever chemicals' because their chemical structures are highly stable and resistant to natural environmental breakdown," Dr. Johnson-Arbor says. "They can persist for years in the environment because of this. Since these chemicals can last for years in the environment, they are found in the water, air, and food that we are exposed to every day."

Exposure to PFAS is a public health concern, according to the CDC. "PFAS chemicals are associated with certain disease processes, including cancer, in animal studies," Dr. Johnson-Arbor says. "But at this time there's not enough evidence to conclusively link PFAS chemicals to diseases in humans. So we don't know with certainty whether PFAS chemicals are toxic to humans (but we know they are found in our bodies and bloodstreams)."

Should You Worry If You've Worn Period Underwear?

Before you freak out about your exposure to period underwear, Dr. Johnson-Arbor assures customers that the situation may not be as dangerous as it seems.

"At this time, we don't have any conclusive data connecting the use of period underwear to adverse health effects," she says. "When used for short periods of time (like during a monthly menstrual cycle), it's likely safe to use period underwear," she says. "However, period underwear is a relatively new concept worldwide, and overall we need more long-term studies to evaluate whether there are any adverse effects associated with the use of these products."

Using consumer products that are "stain resistant" or "water repellent" can expose you to PFAS, according to the Agency for Toxic Substances and Disease Registry, which makes it likely that PFAS would be found in other pairs of period underwear as well. While the vulva is considered a mucous membrane, and therefore it can absorb things more easily than skin on other parts of your body, Dr. Johnson-Arbor reassures that the amount of time spent wearing the underwear makes it less of a concern.

"We don't know exactly how much PFAS can be absorbed through underwear into our bodies, and it's unlikely that the use of PFAS underwear for just a few days a month would lead to a significantly increased human exposure to these chemicals, especially considering that we are exposed to PFAS through other routes as well (including food and water)," Dr. Johnson-Arbor says. Similarly, studies specifically dealing with the toxicity of nanoparticles are still scarce and typically focus on inhaled nanoparticles.

How Do I Know Which Period Products to Trust?

When this kind of news pops up, it can feel challenging to know who to trust. Ali Schwebel, CEO of Vibrant Body Co. suggests the below to get the answers you need:

  • Look for third-party certifications. Check the brand's website, social media, and packing for OEKO-TEX and GOTS Certified labels. Both of these certifications certify that the product has been tested for harmful substances to protect the health of the consumer. "Look for third-party certifications instead of relying on just what [the brand is] saying," she says. "Unfortunately, because of the lack of regulation in the US, it can be difficult to break through the 'clean-washing' so that is why third-party certifications can be so important."
  • Keep away from certain keywords. A lot of PFAS are found in brands that use claims like "stain-resistant" "waterproof," and "shrinkproof." That's because they rely on the chemicals that maintain the fabric. "I know you can find waterproof fabrications that are OEKO-Tex certified," Schwebel encourages.
  • Wash intimates before you wear them for the first time. While it won't get rid of the chemicals entirely, cleaning clothes before wearing them reduces exposure to any chemicals leftover from manufacturing. "Personally, I always wash my clothes before I wear them," Schwebel says. "Experts agree that doing so can help to remove the levels of potential irritants."
  • Ask questions. A transparent company should welcome questions about its practices. Schwebel suggests asking: What certifications do you have? What chemicals will never be in your products? How do you test? Demand to know more about the testing done to ensure the products are free of harmful substances and safe to wear.

Dr. Johnson-Arbor added that if people have questions about the toxicity of PFAS chemicals, they can contact poison control for expert advice. There are two ways to contact poison control in the United States: online at or by phone at 1-800-222-1222. Both options are free, confidential, and available 24 hours a day.