Thinx Leak-Fighting Cotton Brief Underwear
Don't buy until Thinx reveals the gusset treatment material or obtains third-party verification.
This underwear has a waterproof gusset, but Thinx won't say what coating is used. Waterproof textile treatments have historically contained PFAS.
The safe swap
Kotex
Kotex Core Daily 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 blend with waterproof gusset coating (unspecified)
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
What we don’t know
- Basis
- Model estimate, 42% 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.