The Knix PFAS lawsuit was a 2023 class action, Spencer v. Knix Wear, Inc., that accused the Canadian leakproof underwear brand of falsely marketing its period products as free of PFAS “forever chemicals.” It settled for more than $1.4 million, with eligible U.S. buyers able to claim up to $15.90 in cash and Knix agreeing to expanded testing of its finished garments. The claims deadline was March 11, 2024, and the court granted final approval on April 24, 2024.1Justia. Spencer et al v. Knix Wear, Inc. et al, Filing 52
What the Lawsuit Alleged
Knix had marketed its leakproof underwear, tights, swimwear, and reusable pads with claims like “PFAS free,” “100% free of PFAS, fluorine and toxic chemicals,” “fluorine free,” “tested and cleared for harmful substances,” and “OEKO-TEX® certified.”2Truth in Advertising. Spencer v. Knix Wear Complaint Plaintiffs Erin Spencer and Nickole Gonzalez said those claims were false.
Their complaint pointed to independent testing published by the consumer health site Mamavation in May 2021. Using an EPA-certified lab, Mamavation measured total fluorine as a proxy for PFAS in two Knix styles. Knix Boyshorts came back at 43 parts per million; the Knix High Rise came back at 373 ppm.3ClassAction.org. Thinx Underwear Toxic Chemicals Lawsuit Mamavation treated 100 ppm as the line above which PFAS looked to have been intentionally added.4Mamavation. Period Underwear Contaminated PFAS Chemicals
The plaintiffs argued that the third-party labs Knix relied on used detection limits too high to catch PFAS that more sensitive methods could pick up. Because of the “PFAS free” marketing, they said, consumers paid a premium they otherwise would not have paid, or would have skipped the products entirely.2Truth in Advertising. Spencer v. Knix Wear Complaint
The complaint also challenged the OEKO-TEX® label. Plaintiffs said Knix never disclosed which specific OEKO-TEX® certification its fabrics carried, and that a search of the OEKO-TEX® Buying Guide turned up no certification for Knix at any production stage. Knix had told Consumer Reports its products complied with OEKO-TEX Standard 100, but that standard screens for only a fraction of the thousands of PFAS compounds in use.5Environmental Working Group. New Lawsuit Contends Period Products Contain Forever Chemicals
PFAS, short for per- and polyfluoroalkyl substances, are called “forever chemicals” because they resist breaking down and accumulate in the body and the environment. Exposure has been linked to period irregularities, ovarian disorders, high blood pressure during pregnancy, and low birthweight.6Harvard T.H. Chan School of Public Health. Questions Raised About PFAS in Period Products Period underwear sits against skin in a sensitive area for hours at a stretch, which is why researchers and advocates have singled out these products for scrutiny.
Who Was Covered and What the Settlement Paid
The settlement class included U.S. consumers who bought Knix leakproof or super leakproof underwear, tights, swimwear, or reusable pads between January 1, 2020 and December 31, 2022.7Top Class Actions. Knix Toxic Chemicals $1.4M Class Action Settlement
The fund started at more than $1.4 million, with Knix agreeing to add up to $600,000 more if claims outran the initial pool.3ClassAction.org. Thinx Underwear Toxic Chemicals Lawsuit Eligible class members could claim up to $5.30 per product for up to three products, capping individual payouts at $15.90.7Top Class Actions. Knix Toxic Chemicals $1.4M Class Action Settlement
The claims window has closed. It ran through March 11, 2024, and the KNS Settlement Administrator handled distribution.7Top Class Actions. Knix Toxic Chemicals $1.4M Class Action Settlement1Justia. Spencer et al v. Knix Wear, Inc. et al, Filing 528CourtListener. Spencer v. Knix Wear, Inc. Docket
What Knix Agreed to Change
Beyond the cash fund, Knix committed to keep PFAS out of its production processes and to prove it with more testing. The company agreed to continue taking measures to ensure PFAS are not intentionally added at any stage of manufacturing, and for a two-year period to increase the frequency of PFAS and fluorine testing on finished products.3ClassAction.org. Thinx Underwear Toxic Chemicals Lawsuit
The Earlier Case That Was Dismissed
If you’ve come across an earlier suit against Knix, that was a separate case. On April 4, 2022, plaintiffs Gemma Rivera and Marisa Franz filed Rivera et al. v. Knix Wear, Inc. in the Northern District of California, raising California consumer-protection, warranty, and fraud claims along with a federal Magnuson-Moss Warranty Act count.9Bloomberg Law. Knix Wear Sued Over PFAS Chemicals in Menstrual Underwear It never reached a ruling. Both plaintiffs voluntarily dismissed their claims, Franz with prejudice on September 1, 2023, each side eating its own fees.10ClassAction.org. Rivera et al. v. Knix Wear Inc. Dismissal The Spencer complaint was filed the same day in New York.8CourtListener. Spencer v. Knix Wear, Inc. Docket
Where Knix Stands Now on PFAS
On its public product safety page, Knix says it does not intentionally use PFAS in making its leakproof products and contractually bars suppliers from adding them. Suppliers must guarantee their materials are free of added PFAS and run their own quality-control testing for PFAS and fluorine.11Knix. Product Testing Safety
The company says routine PFAS testing began in January 2020 and now covers both raw fabrics and finished garments. As of August 2025, Knix reported no PFAS or organic fluorine detected at testing limits of 0.01 to 1 ppm for individual PFAS compounds and 20 ppm for organic fluorine.11Knix. Product Testing Safety The company also acknowledges that because PFAS are present in water, air, and soil, it “cannot promise that a product will make it to customers PFAS free,” and that trace levels may appear through supply-chain processes.12Knix. Product Testing Safety
Period Underwear and PFAS Beyond Knix
The Knix case sits inside a wider wave of period-underwear litigation. Thinx, a direct competitor, drew scrutiny beginning in 2020 after independent tests found fluorine levels as high as 3,264 ppm in its products, and settled its own class action for between $4 million and $5 million.3ClassAction.org. Thinx Underwear Toxic Chemicals Lawsuit
Academic testing has echoed the same concern. A 2023 University of Notre Dame study of 44 period and incontinence products found that nearly half had fluorine levels suggesting unintentional PFAS contamination, and eight had levels high enough to suggest PFAS-treated material had been intentionally added.13The New York Times Wirecutter. Forever Chemicals in Period Incontinence Products A 2025 study in Environmental Science & Technology Letters tested 59 reusable feminine hygiene products and found evidence of intentional fluorination in 33 percent of period underwear and 25 percent of reusable pads. Because at least one product in each category contained no intentional fluorine, the researchers said PFAS in these products is unnecessary.14ACS Publications. PFAS in Reusable Feminine Hygiene Products
Period products in the U.S. are not rigorously tested by the FDA for chemical content, and manufacturers are not required to disclose every material used in them.6Harvard T.H. Chan School of Public Health. Questions Raised About PFAS in Period Products That gap is a large part of why consumer testing and class actions, rather than regulators, have driven what the public now knows about PFAS in these products.