Flex Review, Is Flex Non-Toxic?
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.
Across 7 graded products, Flex averages Good (70/100). On disclosure, the brand says nothing publicly about PFAS. 7 of its products grade Good or better. Grades are model-based estimates, not lab results.
Worth buying from Flex Good or better, safest first
Flex
Cup Starter Bundle
Medical-grade silicone, no added Teflon-family coating
Residual manufacturing compounds / silicone impurities
Medical-grade silicone undergoes purification, but trace volatile organic compounds or…
Mold or bacterial colonization from improper storage
This is a user-maintenance issue, not a product defect. Storing the cup in an airtight…
Lower concern, silicone menstrual cups have minimal PFAS exposure pathways, but Flex hasn't publicly disclosed testing.
⚠Risky category by default
Flex
Menstrual Discs
Medical-grade silicone
Silicone degradation and particulate shedding
Medical-grade silicone is stable under normal use, but micro-tears from insertion…
Allergen/irritant sensitivity to silicone additives
Silicone manufacturing may involve trace residual catalysts or plasticizers; individuals…
Bacterial colonization from improper cleaning
Any reusable menstrual device poses low but documented risk of bacterial overgrowth if…
Off-gassing or odor from manufacturing residues
New silicone products may emit subtle odors from curing agents or mold release compounds…
Lower concern since silicone-based period product has no known PFAS risk, but brand provides no transparency.
⚠Risky category by default
Flex
Cup Menstrual Slim Pack of 1
Medical-grade silicone
Bacterial or mold colonization from poor maintenance
Any menstrual cup can harbor bacteria or fungal growth if not cleaned thoroughly between…
Contaminants from manufacturing residue
Silicone cups may retain manufacturing lubricants, mold-release agents, or dust if not…
Lower-concern product since silicone menstrual cups rarely require PFAS treatments.
⚠Risky category by default
Flex
Reusable Menstrual Cup | Flex Cup Size 01
Medical-grade silicone
Bacterial or fungal colonization
Any reusable menstrual cup can harbor bacteria or fungi if inadequately cleaned or stored…
Allergic contact dermatitis or sensitization
Rare reports of irritation or allergy to silicone cups exist in medical literature…
Lower PFAS concern, medical-grade silicone has no known PFAS need, but Flex doesn't publicly address it.
⚠Risky category by default
Flex
Reusable Menstrual Disc
medical-grade silicone
Bacterial or fungal contamination
While silicone itself resists microbial biofilm better than latex, improper storage (damp…
PFAS
Some medical-grade silicone suppliers may use PFAS in processing or as mold-release…
Loss of elasticity and structural failure
Users report occasional cracking or loss of flexibility after 1-3 years of use…
Lower-concern choice since silicone isn't a PFAS vector, but brand offers no transparency.
⚠Risky category by default
Flex
Silicone Menstrual Cups
Medical-grade silicone (body-contact surface)
Bacterial or fungal biofilm growth on cup surface
If cups are stored wet or in airtight containers, or not fully dried after cleaning…
Surface degradation or discoloration over extended use
User reports document yellowing or slight surface roughening after 2-3 years of use…
PFAS
Flex does not publicly disclose PFAS testing or supplier audits. Medical-grade silicone…
Lower-concern product since silicone cups don't require PFAS-prone treatments, but manufacturer silence on sourcing limits full confidence.
⚠Risky category by default
Flex
Menstrual Cup
Medical-grade silicone
Silicone degradation and particle shedding
Medical-grade silicone can degrade if exposed to very high heat, harsh chemicals, or…
Microbial contamination (bacterial or fungal growth)
If the cup is not boiled regularly, stored in a damp environment, or dried incompletely…
Lower PFAS concern since menstrual cups have no functional PFAS need, but Flex doesn't publicly disclose sourcing or testing.
⚠Risky category by default
Every grade uses the same public rubric. How grades work →