Thinx Leak-Fighting Rotation Set Underwear
Don't buy until the brand reveals the waterproof coating material; period underwear's leak-fighting layer is a common PFAS concern.
Thinx does not reveal what chemical makes this underwear waterproof. Period-care garments rely on waterproof barriers that frequently contain PFAS.
The safe swap
Kotex
Kotex Wrapped Liners
70/100 safety
Same rubric that flunked this product. The swap earned Good.
Still want this one anyway? Check the price on Amazon. We’d swap it.
Material
Cotton/synthetic blend with waterproof/moisture-wicking coating (unspecified chemistry)
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
What we don’t know
- Basis
- Model estimate, 45% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- Thinx has made none
Formulations change between production runs, so check the current label. How we grade.
Safer alternatives in Panty Liners
Kotex
Core Daily Wrapped Liners
cotton, rayon, adhesive (nonwoven blend)
Synthetic adhesive leachables
Limited concern
Fragrance allergens (if scented variant)
Moderate concern
Microplastic shedding from nonwoven backing
Limited concern
PFAS
Limited concern
Lower PFAS concern; standard period-liner materials without disclosed water-resistance treatment.
⚠Risky category by default
Kotex
Wrapped Liners
Cellulose/cotton absorbent core with adhesive backing
Adhesive skin contact sensitization
Limited concern
Fragrance allergens (if present)
Limited concern
Lower PFAS concern for this product type, but Kotex provides no transparency on coating materials.
⚠Risky category by default
More panty liners grades
How we score: every product runs through the same public 0–100 rubric based on materials, coatings, brand disclosure, lab findings, and recalls. See the full methodology → Spotted a mistake? Report an error.