Does Knix period underwear have PFAS?
Knix period underwear averages 25 out of 100 on PFAS Authority's PFAS and toxin screen across the 8 Knix period underwear products graded as of October 2026, below the 48 out of 100 median for the 21 other period underwear brands graded alongside it.
Knix period underwear averages Poor on our four-band scale. None of them clear our buy threshold. That is above 17% of the period underwear brands we grade.
PFAS Authority is a scoring system, not a laboratory. We do not test products ourselves. Grades are model-based, built from published ingredients, materials, certifications, brand disclosures and third-party lab results where they exist. See the rubric.
What Knix says and does about PFAS
Knix agreed to pay $1.4 million, and up to $600,000 more if needed, to settle a class action over its marketing, and the settlement agreement requires it to remove references to its products being PFAS free from its website. Minnesota’s ban on intentionally added PFAS in menstruation products covers period underwear.
- Legal caseKnix agreed to pay $1.4 million, and up to $600,000 more if needed, to settle a class action over its marketing. Knix settlement site (archived page) ↗
- Legal caseThe Knix settlement agreement requires Knix to revise its website to remove references to its products being PFAS free. Settlement agreement via Truth in Advertising ↗
- Regulatory filingMinnesota’s ban on intentionally added PFAS, in force since 2025, covers menstruation products such as pads, tampons, period underwear and menstrual cups. Minnesota Pollution Control Agency ↗
Sources checked September 14, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.
Graded and flagged Poor and Bad, we’d swap these
Knix
SuperPlus Leakproof No- Show High Rise Underwear
- Cotton/synthetic blend with proprietary waterproof/leak-resistant coating (unspecified)
- Undisclosed waterproof coating chemistry (likely fluorinated or silicone polymer), The proprietary coating is…
2 hazards checked on this product. See all of them.
Knix
Underwear Essential No-Show High Rise Kit
- Cotton-polyester blend with waterproof treatment
- Fluorocarbon/Teflon-type coating in waterproof coating (undisclosed), Knix does not disclose waterproofing…
4 hazards checked on this product. See all of them.
Knix
Women's Super Leakproof Dream Boxers
- Fabric with waterproof/leak-resistant coating (unspecified chemistry)
- Teflon-type coating or fluorochemical fume risk (if Teflon-type coating-based coating), If the waterproof…
4 hazards checked on this product. See all of them.
Knix
Medium-Flow Leakproof Period Underwear
- Organic cotton/viscose with proprietary waterproof coating (unspecified)
- Undisclosed waterproof coating chemistry, Knix does not publicly identify the waterproof polymer or treatment…
3 hazards checked on this product. See all of them.
Knix
Light-Flow Period Underwear
- Absorbent gusset with water-resistant coating, composition unspecified
- PFAS, Unspecified coating on absorbent gusset is typical vector for PFAS in period underwear; brand silence…
5 hazards checked on this product. See all of them.
Knix
Heavy Flow & Bladder Leak Protection Underwear
- Absorbent textile blend with waterproof backing coating, composition unspecified
- Azo dyes in textiles, Conventional cotton-blend fabrics may use azo dyes, which can break down into aromatic…
5 hazards checked on this product. See all of them.
Knix
Heavy Flow & Bladder Leak Protection Underwear Superplus Leakproof No-Show High Rise
- Synthetic blend with unspecified waterproof/leakproof coating
- PFAS, Brand silence on coating chemistry and Poor PFAS grade (25/100) suggest unconfirmed fluorinated…
3 hazards checked on this product. See all of them.
Knix
Leakproof Ultra Thin High Rise Brief
- Fabric with waterproof/leak-resistant coating, unspecified
- PFAS, Knix's PFAS safety score is 25/100, indicating high risk of fluorinated polymers or water-repellent…
4 hazards checked on this product. See all of them.
Better period underwear from other brands
Graded higher than the Knix average of 25.
Ruby Love
Rubylove First Period Kit +teen Period Underwear
- organic cotton, waterproof backing layer
- A third party reports verifying it as PFAS-free
- Coating degradation and microparticle shedding
2 hazards checked on this product. See all of them.
Lunapads
3-Pack BOOST Brief
- organic cotton blend, water-resistant gusset
- The brand calls it PFAS-free, which we have not verified
- Microplastic shedding from water-resistant barrier
Aisle
Super Hipster
- Organic cotton, wood pulp fiber
- The brand calls it PFAS-free, which we have not verified
- Azo dyes and synthetic dyes
2 hazards checked on this product. See all of them.
The same question, asked of the other period underwear brands
Best average grade first. Knix averages 25.
See every Knix product we grade on the Knix brand page, or the full period underwear ranking.