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Period Panty PFAS Problem: Thinx Settles Class Action Lawsuit While Knix Fights Back

Despite denying any and all wrongdoing, Thinx, the underwear brand designed specifically for menstruating women, recently settled a class action lawsuit accusing it of intentionally using per-and polyfluoroalkyl substances, or PFAS.

A website called went up earlier in the week, inviting any and all customers who believe they may have been adversely affected by Thinx clothing to apply to get their share of the $4 million settlement.

In addition to the settlement, Thinx is offering partial buybacks of $7 per piece of underwear with proof of purchase, limit three, and $3.50 per piece without receipt, limit three.

The deadline for claims to be filed is April 12 and a final hearing is set for May 23 in the Southern District Court of New York to establish fairness and finalize the judgment.

Even upon settling, Thinx didn’t admit guilt in the case.

“Thinx denies all of the allegations made in the lawsuit and denies that Thinx did anything improper or unlawful,” the company wrote on the webpage dedicated to the settlement. “With respect to PFAS, Thinx confirms that PFAS have never been a part of its product design, and that it will continue to take measures to help ensure that PFAS are not intentionally added to Thinx Period Underwear at any stage of production. The proposed settlement is not an admission of guilt or wrongdoing of any kind by Thinx.”

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In its original lawsuit, filed in May on behalf lone plaintiff Nicole Dickens, who would wind up standing on behalf of “all others similarly situated,” attorneys argued that the plaintiff’s independent testing “confirmed the existence of harmful chemicals using industry standard testing.”

PFAS, which are known as “forever chemicals,” due to their durability sticking to the item lasting thousands of years, are commonly used in apparel and housewares to create nonstick or stain-proof qualities, the latter of which being useful to the product in question.

Since launching in 2011, the concept of a period-specific panty was met with tremendous response from customers, but also complaints about the expense and durability of the pieces.

In a 2019 article published in WWD, which is owned by the same company as Sourcing Journal, reporter Kellie Ell wrote, “Some customers said the panties didn’t make it to the two-year mark, which is how long they’re guaranteed for. And at almost $40 a pair — (prices range from $24 to $39 for underwear) — the products were expensive. Plus, since each pair has to be hand-washed and dried, that meant women would have to buy multiple pairs, investing hundreds of dollars in their underwear drawers. It might take years to justify the cost.”

Thinx chief brand officer Siobhán Lonergan addressed the challenge of delivering for customers later in the same article.

“We introduced new materials [with Thinx Super] that work better and faster,” Longeran said. “Specifically, the fabric that is closest to your skin, is our moisture wick in there. That’s a new material that wipes moisture faster away from your body. Under that we have a super absorbent layer.”

But at the same time Thinx settled without admitting fault, another maker of underwear for menstruating women, is fighting back hard.

“This consumer protection lawsuit never should have been filed,” defense attorneys for Knix wrote in a November 2022 motion to have all, or at least part of the plaintiff’s case against the underwear maker dismissed. “Plaintiffs have no idea whether any of Knix’s products contain PFAS. Instead they contend – based entirely on anonymous testing reported in a blog called  ‘Mamavation’ published by an affiliate ‘mom-blogger’ who is paid by Knix’s competitors to recommend those competitors’ products – that Knix’s products contain fluorine, which Plaintiffs18  (inaccurately) claim is an ‘indicator’ that the products may also contain PFAS.”

PFAS are scheduled to be outlawed in California and Washington in 2025 and the New York State Assembly is working on measures that would forbid their use in clothing after banning them in carpets as of 2025.

According to the original complaint filed by plaintiffs, the test conducted by Mamavation found that there were 373 parts per million of fluorine found in the Knix underwear. Anything over 100 is considered to be intentionally introduced.

“This is particularly worrisome given the nature of the Products,” plaintiffs argued. “Because the underwear is ‘right up against the vagina’ and rests ‘snug[ly] against the vulva for an extended period of time’ consumers are at a heightened risk of exposure to PFAS.6.”

Knix lawyers went on to write that, “even if the Court declines to sanction Plaintiffs’ counsel for their blind reliance on Mamavation’s report of anonymous testing, the entire FAC still must be dismissed because Plaintiffs fail to plausibly allege that the Knix products they purchased contain fluorine, much less the type of fluorine that can indicate the presence of PFAS.”

Plaintiff’s attorneys fired back last week, a full month before the parties are set to go before the Hon. Edward J. Davila in Northern District Court of California on Feb. 10.

They appealed to a ruling from a December 2022 case, when Judge William H. Orrick of the Northern District Court ruled that part of the plaintiff’s lawsuit could stand in the case of a class action suit against Walmart even after the defendant challenged third-party testing of herbs and spices sold by the nation’s largest retailer that contained dangerous levels of heavy metals.

Judge Davila will hear the motions from both sides on Feb. 10 and may rule to throw out some, none or all of the 15 counts brought against Knix, which include fraudulent inducement and violation of California’s false advertising law.

Neither Thinx nor attorneys for Knix have responded to Sourcing Journal’s request for comment.