Does Knix Have PFAS? The 2021 Lab Test, the 2024 Settlement and Knix's 2026 Results

Does Knix have PFAS? Independent lab screens posted in 2021 and later found fluorine, a PFAS marker, in three Knix styles bought in 2020. A separate class action alleging PFAS in some samples settled in 2024 with no admission; the agreement says it concerned marketing claims, not unsafe products. Knix's August 2026 results report no PFAS or organic fluorine detected at its lab's limits. Nobody can confirm what is in a specific pair, and neither can a label scan.

What the 2021 Mamavation Test Found on Knix

The only outside testing of Knix products with published numbers that we could find comes from Mamavation, a consumer-health and wellness site, not a regulator, whose page uses affiliate links. According to Mamavation's Knix lab results page, first published July 14, 2021, the site sent Knix underwear to what it calls an EPA-certified laboratory, which it does not name. The page says the pairs were bought between May and December 2020, with packaging unopened.

The method was "Total Fluorine by Oxygen Flask Combustion and Ion-Selective Electrode," with a detection level of 10 parts per million (ppm). The page now lists three results: 373 ppm of fluorine in the High Rise style, 43 ppm in the Boyshorts and 17 ppm in the High Waisted. The High Waisted figure was added after the first post; the page marks it "new results added."

Mamavation was critical of the brand's marketing, which the page quotes as "100% free from PFAS." The page carries no response from Knix and no repeat test of any Knix style. We read Alo's record the same way: one outside screen plus a legal file, each taken for what it shows.

What a total fluorine number can and cannot tell you

Total fluorine counts fluorine atoms in a sample. A high number signals that fluorinated chemistry may be present, but it does not name a compound or measure any specific PFAS. Targeted tests work the other way around: they look for a fixed list of named compounds and report each against its own limit.

The two can disagree by a wide margin. In a peer-reviewed study of North American school uniforms, Xia and colleagues measured both and wrote that "there is still a large gap between concentrations of fluorine from PIGE and from the targeted analysis." PIGE was their total fluorine method. Knix takes a third position. According to Knix's testing page, the relevant screen is organic fluorine. Its reason is that inorganic fluoride occurs naturally in minerals and "does not indicate the presence of PFAS." Each method answers a different question.

The Lawsuits: Two Separate Cases

The phrase "Knix PFAS lawsuit" covers two different cases. They had different plaintiffs, different courts, different evidence and different endings, so it helps to keep them apart.

The California case

Rivera v. Knix Wear, Inc. (N.D. Cal., No. 5:22-cv-02137) was filed on April 4, 2022, according to the court docket. Its amended complaint, filed three days later, cited "independent research conducted by Mamavation and an EPA-certified laboratory" and the 373 ppm fluorine result. In June 2022, Knix moved to dismiss the case and filed a motion asking the court to impose sanctions under Rule 11.

According to a July 2023 court order, the judge took those motions under submission on February 6, 2023, without oral argument. The court never ruled on them. The docket shows the two plaintiffs dismissing their claims themselves, one in August 2023 and the other on September 1, 2023. The case ended because the plaintiffs dropped it, not because of any decision on the merits.

The New York case

Spencer v. Knix Wear, Inc. (S.D.N.Y., No. 1:23-cv-07823) is the case that settled. Its complaint was filed on September 1, 2023, and the proposed settlement agreement was filed with the court the same day. The complaint rests on "Plaintiffs' independent testing" from "a third-party lab." It names no lab, publishes no test figures and does not mention Mamavation. The court records we found are U.S. federal cases.

What the 2024 Settlement Says, and What It Does Not

On April 24, 2024, Judge Jennifer L. Rochon of the Southern District of New York granted final approval. The final approval order states that "the Settlement Agreement is fair, reasonable and adequate." That is a judgment about the deal. The order does not decide whether the allegations were true, and it says nothing about product safety.

So what were the allegations? According to the settlement agreement, the plaintiffs alleged that Knix's marketing represented the products as "100% free of" PFAS, fluorine and toxic chemicals. They said some samples tested by their counsel contained PFAS detectable "using more sensitive testing methods with lower detection limits" than Knix's labs used. The agreement then draws a clear line: "Plaintiffs' claims involve Knix's marketing statements; they do not involve allegations that any Knix products are unsafe and/or cause injuries, or that Knix intentionally added PFAS to its products."

Knix's side is in the same document. It denies the allegations and any wrongdoing, and denies ever intentionally using PFAS to make the products. It says it stands behind the safety of its products and its testing disclosures. It does not concede that the plaintiffs' results show PFAS, and says any amounts were trace levels "at or near the limit of what is currently detectable." It also acknowledges that trace PFAS may show up in a consumer product even when none was intentionally added.

The money was modest per person. Knix agreed to a $1.4 million minimum fund, up to $600,000 more if valid claims required it, and a $2 million cap. Eligible buyers could receive $5.30 per pair for up to three pairs, or $15.90 at most. The class covered U.S. purchases from January 1, 2020, to December 31, 2022. Covered products were Knix leakproof and super leakproof underwear, plus KnixTeen leakproof underwear, super leakproof underwear, leakproof tights, leakproof swim and reusable pads. Claims were due within 90 days after notice went out, and that window has closed.

What Knix agreed to change

Knix agreed to continue its measures so that PFAS are not intentionally added to its products. For two years from preliminary approval, granted on October 30, 2023, Knix would test finished products for PFAS and fluorine twice a year instead of once. It would also require its fabric suppliers to test for PFAS and organic fluorine twice a year instead of once.

For one year, Knix would keep "PFAS Free," "Toxic Chemical Free" and "Fluorine Free" claims off its website; the agreement notes Knix had already revised that page before signing. Knix stayed free to publish its test results. And the agreement states that settling is "not an admission of guilt or wrongdoing of any kind."

Does Knix Have PFAS Now? What Knix's 2026 Results Show

If you are looking for Knix PFAS 2026 data, the main public source is Knix itself. Its testing and safety page, headed "August 2026 / Team Knix," is company-reported, so read it as Knix's account of its own testing. Knix says it began routine PFAS testing of its leakproof fabrics and products in January 2020, and organic fluorine testing "shortly thereafter."

Knix says its targeted PFAS limits are 0.01 to 1 ppm (10 to 1,000 parts per billion, or ppb) per chemical, aligned with the AFIRM Group Restricted Substances List. Its organic fluorine screen is benchmarked at 20 ppm. The page states that "neither PFAS nor organic fluorine was detected at the testing limits."

The August 2026 summary table, marked "Prepared by Knix," covers seven black items. They are the SuperPlus Leakproof Dream Short, Super Leakproof Dream Boxer, Leakproof UltraThin No-Show Boybrief, Period Swim Board Shorts, Leakproof Sculpt Swim Short, Leakproof Contour Thigh Saver and Super Leakproof Reusable Snap Pads (Overnight). Every entry reads ND, for not detected. The table lists several dozen named PFAS compounds and their salts, including PFOS, PFOA, PFHxS and PFHxA, at reporting limits of 10 or 100 ppb, plus total fluorine and total organic fluorine at 20 ppm. The individual lab sheets, dated August 11 and 12, 2026, mark the results "Meet Buyer's Requirement." Older result tables, including ones headed December 2023, July 2024, December 2024 and July 2025, are posted too.

So does Knix still have PFAS? Read these results for exactly what they say. "Not detected" means below that limit, not zero. That is a fixed list of named compounds plus fluorine screens, not every one of the thousands of PFAS. Knix chose which results to post and commissioned the testing from outside labs it does not name, so this is not independent verification.

And is Knix period underwear PFAS free? Knix does not make that claim. It says it does not intentionally use PFAS in making its leakproof products, and adds: "Knix, or any company for that matter, cannot promise that a product will make it to customers PFAS free."

Why the 2021 and 2026 Numbers Do Not Line Up

It is tempting to set 373 ppm next to "not detected" and pick a winner. The two records do not measure the same thing, so they cannot cancel each other out.

They differ on four counts. The years differ: Mamavation tested pairs bought in 2020, while Knix's latest sheets cover samples tested in August 2026. The products differ: three underwear styles then, seven leakproof and swim items now. The methods differ: total fluorine then, targeted compounds plus total and organic fluorine screens now. And the floors differ.

That last point matters more than it looks. Mamavation's detection level was 10 ppm total fluorine, while Knix's fluorine screen floor is 20 ppm. So Mamavation's 17 ppm High Waisted reading would have been reported as not detected by a 20 ppm test. The same logic ran the other way in the New York case, where the plaintiffs said their methods had lower detection limits than Knix's labs.

None of this proves either side wrong. Mamavation's screens and Knix's 2026 results answer different questions about different samples, years apart. The useful question is narrower: what was tested, when, by which method and down to what level.

What This Means for the Pair in Your Drawer

Start with the health context, kept short. According to the EPA, there are thousands of PFAS chemicals, exposure to some PFAS in the environment may be linked to harmful health effects, and how much people are exposed is still being studied. The ATSDR says epidemiological evidence suggests associations between some PFAS and effects such as higher cholesterol and a lower antibody response to some vaccines, and that research is ongoing.

None of the Knix records, from Mamavation's screens to the court filings to Knix's results, measured how much PFAS, if any, passes from a garment into the body. An American Chemical Society summary of a 2025 study on reusable period products says knowledge of how PFAS are absorbed through skin is still limited; that coverage names no brands. For what tests found across period underwear brands, see our period underwear PFAS guide.

If you own Knix leakproof underwear, here is a practical way to read the record:

• Note when you bought the pair: the 2020 to 2022 class period or current stock.
• Read the scope of any posted test: which items, which compounds, which limits.
• Ask Knix for results on your exact style if it is not in the posted tables.
• Bras and non-leakproof lines have no published data from either side, so the record says nothing about them either way.

One more limit. A label lists fibers, not finishes, and neither a label nor an app can see a PFAS treatment; for that you need the brand's test results and their scope. Stretch fibers such as spandex are not PFAS, as our spandex guide explains; the PFAS question in period underwear is about treatments, not the stretch fiber.

FAQ