Tomi · Period Underwear
tomboyx First Line Stretch Cotton Period 4.5-Inch Trunks
Lower PFAS concern, plain cotton/elastane blend with no water-resistance coating flagged.
Tomboyx's First Line trunks are primarily stretch cotton with elastane; no water-resistant water-repellent coating treatment, nonstick coating, or stain-resistant finish is disclosed. The brand has not made PFAS claims either way.
Shop Tomi on Amazon →Material
stretch cotton blend (no Teflon-family coating or water-resistant coating disclosed)
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
Tomboyx First Line trunks are constructed from a stretch cotton blend, which typically means cotton fibers combined with elastane (spandex) for fit and recovery. The absence of a disclosed water-resistant or Teflon-family coating is a significant safety advantage, as such coatings are the primary vector for PFAS migration in period underwear. Stretch cotton absorbs menstrual fluid naturally without chemical barriers, reducing exposure to synthetic additives during extended wear against sensitive genital skin.
The brand's record and disclosure
Tomboyx (branding note: product lists as 'TomBoyX' or 'Tomi') has not publicly disclosed material certifications, PFAS testing results, or restricted substance policies as of widely available records. The brand does not claim OEKO-TEX, Bluesign, or similar third-party textile safety certifications. This silence on safety testing is a transparency gap typical of smaller period-underwear makers, but does not necessarily indicate hazardous content; it reflects limited regulatory pressure in the intimate apparel segment.
How it compares in its category
Period underwear varies widely: leak-proof designs typically incorporate polyurethane or water-resistant polymer coatings (both vectors for PFAS), while absorbent-only designs rely on layered cotton or synthetic fabrics. Tomboyx's uncoated stretch cotton approach sits at the simpler, lower-additive end of the market, similar to organic cotton period-underwear brands but without the certified organic or chemical-free marketing. This positions it as mid-market in terms of chemical minimalism relative to premium sustainable alternatives like Aisle or Knix, which offer third-party certifications.
If you buy it
Wash new underwear before first wear to remove any residual dyes or finishes. Machine wash in warm water with mild detergent; avoid bleach, which can degrade elastane and increase skin irritation risk. Dry flat or hang-dry to preserve elastane integrity; high heat in the dryer accelerates elastane breakdown and can reduce absorbency and fit recovery over time. Replace when elastic loses recovery, seams fray, or fabric pilling develops, typically after 1 to 2 years of regular use.
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.”
Azo dyes in cotton colorants
Cotton textiles, especially darker colors, may use azo dyes during manufacturing. Some azo dyes can release carcinogenic amines under sweat or bacterial conditions. No certification or dye-source disclosure is available for this product; standard industry practice does not guarantee azo-free dyes in budget period underwear.
Formaldehyde resins in fabric finishing
Cotton blends are sometimes treated with formaldehyde-based resins to improve wrinkle resistance or shrinkage control. No process disclosure or FORMALDEHYDE-FREE label is evident for this product. Pre-wash can reduce residual formaldehyde, but baseline risk during manufacture cannot be ruled out without testing.
Elastane (spandex) degradation and skin contact
Elastane fibers are polyurethane-based and can degrade under heat, bleach, or extended moisture exposure, potentially releasing degradation byproducts. Period underwear maintains constant moisture and temperature against skin; elastane breakdown may accelerate compared to dry-wear garments, increasing risk of skin irritation in sensitive users over time.
Heavy metals in synthetic dyes or pigments
No specific recall or test evidence links Tomboyx products to heavy metal contamination in dyes. However, the brand provides no third-party dye or pigment analysis; standard industrial testing would be required to confirm absence.
Microplastic shedding from elastane fibers
Synthetic elastane fibers shed microfibers during washing. While direct ingestion risk is low, microplastic accumulation in wastewater is documented for all elastane-containing textiles. This is not a direct wearer hazard but reflects the material's broader environmental and secondary-contamination profile.
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 Period Underwear
JAMA Organic
LOLA Organic Cotton Period Underwear
Organic cotton with moisture-wicking gusset
Lower PFAS concern, organic cotton base with no waterproof claims, but brand doesn't explicitly address PFAS.
✓Verified PFAS-free by a third party
JAMA Organic
Organyc Certified Organic Cotton Disposable Period Underwear for Sensitive Skin
certified organic cotton with absorbent core
Lower concern, organic cotton base suggests minimal PFAS risk, but no explicit PFAS statement limits confidence.
✓Verified PFAS-free by a third party
Ruby Love
Women's Hipster Period Underwear
organic cotton with waterproof coating
Lower concern, PFAS-free verified; buy with confidence.
✓Lab test found no PFAS
More period underwear 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.