Flex · Menstrual Cups
Flex Cup Menstrual Slim Pack of 1
Lower-concern product; silicone menstrual cups rarely require PFAS treatments.
Flex Cup is a medical-grade silicone menstrual cup with no known PFAS-treatment applications. Silicone doesn't inherently require Teflon-family coating coatings, water-repellency treatments, or stain resistance. Flex has not publicly disclosed PFAS testing or claims, but the material category itself carries minimal traditional PFAS risk.
Shop Flex on Amazon →Material
Medical-grade silicone
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
Why this grade
Category baseline
period care is a category where PFAS exposure is more common.
No PFAS disclosure
No public statement about PFAS in this product.
Safe base material
Made from a material with no inherent PFAS use (ceramic, mineral, or natural fiber).
The full breakdown
What it's made of and why it matters
Flex Cup is constructed from medical-grade silicone, a synthetic polymer engineered for biocompatibility and durability in devices that contact mucous membranes. Medical-grade silicone is chemically inert at body temperature and does not leach estrogen-mimicking compounds like BPA, which disqualifies it from most plastic food-storage hazards. The material is non-porous, resistant to bacterial colonization compared to natural rubber, and designed to withstand repeated sterilization without degradation. Silicone menstrual cups historically do not require PFAS water-repellency or stain-resistance treatments because the material's inherent properties meet functional needs.
The brand's record and disclosure
Flex has not publicly disclosed detailed chemical composition or third-party safety testing results for the Flex Cup in accessible consumer materials, which is typical for smaller menstrual-product brands. The company does not appear on any major product-safety recall databases for menstrual cups. Flex markets the cup as FDA-cleared medical device, indicating baseline regulatory oversight, though FDA clearance focuses on mechanical safety and sterility rather than chemical purity. No established controversies or litigation regarding the Flex Cup's material safety have surfaced in public record.
How it compares in its category
Menstrual cups as a category are considered lower-chemical-risk period products compared to tampons and pads, which may contain rayon blends, fragrance, chlorine bleaching byproducts, and adhesive residues. Silicone cups outperform natural-rubber latex alternatives on allergy and leaching concerns, though latex cups are still considered safe for most users. Flex Cup's single-pack format is comparable to Saalt, Diva Cup, and store-brand silicone alternatives in material safety profile. No published independent testing distinguishes Flex Cup from competitors on chemical safety metrics.
If you buy it
Boil the cup for 5-10 minutes before first use and between cycles to eliminate any manufacturing residue and maintain sterility. Store in a breathable container (not sealed plastic) to prevent mold growth; the included pouch or a cotton drawstring bag works well. Replace the cup if you notice sticky residue, odor that does not wash away, visible cracks, or discoloration; medical-grade silicone typically remains safe for 5-10 years with proper care. Avoid prolonged exposure to direct heat (dishwasher safe on low, but air-dry is gentler); silicone does not degrade at body temperature but may yellow over time without affecting function.
Beyond PFAS: other things we checked
Established hazard classes for this product type, assessed from public information. These never change the PFAS grade; a Likely flag caps the Verdict at “Buy with care.”
Silicone leaching or degradation
Medical-grade silicone used in menstrual cups and implants has no established record of leaching harmful oligomers or degrading into toxic compounds during vaginal use at body temperature. Long-term safety data from decades of silicone breast implants and medical devices supports inertness.
Bacterial or mold colonization from poor maintenance
Any menstrual cup can harbor bacteria or fungal growth if not cleaned thoroughly between uses or stored in a damp, sealed environment. Silicone's non-porous surface is actually advantageous here compared to natural rubber, but user neglect remains a practical risk.
Allergic sensitization or irritation
Medical-grade silicone is hypoallergenic and does not contain common allergens like latex, accelerators, or fragrance. No reported cases of silicone menstrual cups triggering contact dermatitis or sensitization have surfaced in clinical or consumer reports.
Contaminants from manufacturing residue
Silicone cups may retain manufacturing lubricants, mold-release agents, or dust if not rinsed or boiled before first use. A single boil step before use mitigates this risk substantially, though Flex provides minimal transparent guidance on pre-use preparation.
Absorption of fragrance or topical product residues
Silicone is non-porous and does not absorb vaginal fluids, lubricants, or topical medications the way tampons do, eliminating this category of chemical contamination risk entirely.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 78% confidence. It is not a lab result.
No independent PFAS lab test is on record for this exact product. A lab test could move the score in either direction.
The brand has not made a specific, verifiable PFAS-free statement, so part of this score reflects that missing disclosure rather than a confirmed material.
Formulations and coatings change between production runs. Always check the current label before buying.
Safer alternatives in Menstrual Cups
Aisle
DIVA Cup Model 2
Medical-grade silicone (body); no Teflon-type coating or Teflon-family coating coatings
Lower-concern menstrual cup; silicone construction and PFAS-free commitment make it a reasonable choice.
✓Verified PFAS-free by a third party
Ruby Cup
Steriliser
Stainless steel heating chamber with silicone/plastic components
Lower-concern menstrual cup sterilizer; stainless core typical for appliances, but silicone/plastic parts unspecified, contact brand for material detail.
⚠Risky category by default
Ruby Cup
Steriliser Purple
stainless steel steriliser/heating element
Lower PFAS concern; no high-risk coatings typical of this product category.
⚠Risky category by default
More menstrual cups 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.