The average woman uses approximately 11,000 tampons or pads in her lifetime. She is rarely told what is in them. She is not informed that the cotton is likely non-organic — meaning it was grown with heavy pesticide application, and may carry glyphosate residues. She is not told that the bleaching process that makes tampons white creates dioxin byproducts. She is not told that the vaginal mucosa — the tissue these products are in direct contact with — is among the most absorptive tissue in the human body.
What enters through vaginal tissue bypasses the liver's first-pass metabolism. It goes systemic faster, at higher effective concentrations, than the same substance swallowed. This is not a feature — it is a mechanism that makes what you put near this tissue a category of its own.
Tampons and pads are classified as medical devices in the US, but manufacturers are not required to disclose all ingredients. The FDA does not require a full ingredient label. What follows is what independent testing and published research have found in conventional products.
Glyphosate & AMPA (Monsanto's Roundup)
A 2015 study by Argentine researchers (commissioned by SENASA, the national food safety authority) tested 13 brands of cotton-based personal care products — tampons, gauze, cotton balls, and swabs. Glyphosate and/or its primary metabolite AMPA were detected in 85% of all samples. The brands included market leaders sold in the US and Europe. Non-organic cotton is one of the most heavily glyphosated crops in agriculture — and glyphosate does not fully wash out of fiber. The FDA does not require testing of glyphosate residues in tampons.
Dioxins & Furans — from Chlorine Bleaching
Conventional tampons and pads use cotton and rayon that is bleached white using chlorine or chlorine dioxide. This process creates organochlorine byproducts including dioxins and furans — among the most toxic compounds known. The FDA's position: levels are "below detectable limits" and therefore safe. The WHO's position on dioxins: they are highly toxic, carcinogenic, immunotoxic, and have no safe exposure threshold — meaning any detectable level in tissue represents accumulation. Dioxins are lipophilic — they store in fat tissue, including ovarian and breast tissue, and do not clear quickly.
Rayon (Viscose) — Synthetic Wood Pulp Fiber
Most tampons use a cotton-rayon blend. Rayon is made from wood pulp treated with carbon disulfide and other industrial chemicals. It is more absorbent than cotton — which contributed to the Toxic Shock Syndrome crisis of the 1980s. Superabsorbent rayon fibers create anaerobic micro-environments hospitable to Staphylococcus aureus and the TSST-1 toxin responsible for TSS. The 1980 Rely tampon recall (Procter & Gamble) was directly driven by this mechanism. Rayon production involves chemicals including carbon disulfide, sodium hydroxide, and sulfuric acid — residues have been detected in finished products.
Synthetic Fragrance — in "Fresh Scent" Products
Scented pads and tampons contain synthetic fragrance — a legally protected trade secret that can contain dozens of undisclosed chemicals including phthalates (endocrine disruptors), musks (carcinogens), and volatile organic compounds. Applied directly to vulvar and vaginal tissue — some of the thinnest, most permeable skin on the body — these compounds are absorbed systemically. Fragrance in intimate care products is also associated with vulvodynia, contact dermatitis, and vaginal microbiome disruption. There is no functional benefit. The odor being "corrected" is the natural scent of a healthy vagina.
BPA & BPS in Plastic Applicators
Plastic tampon applicators are typically made from polyethylene or polypropylene. Independent testing has found BPA (bisphenol A) and its replacement BPS in various plastic tampon applicators. Both are estrogenic endocrine disruptors. BPS, widely substituted for BPA after its dangers became public, has been shown to be equally or more disruptive to hormonal signaling than BPA. Cardboard applicators eliminate plastic exposure; applicator-free tampons eliminate it entirely.
Pesticide Residues — Beyond Glyphosate
Cotton is treated with multiple pesticides in conventional agriculture: malathion, chlorpyrifos (a neurotoxin the EPA tried to ban before being overruled), permethrin, and others. Testing of finished cotton products has found residues of multiple compounds. None are required to be disclosed on the label. Organic cotton is grown under USDA Certified Organic standards with prohibited pesticide lists — not a perfect system, but a meaningful reduction in chemical load.
Period underwear was marketed as the toxin-free, sustainable alternative to conventional disposables. Then independent testing revealed what the ingredient label didn't say.
PFAS Detected in Multiple Period Underwear Brands
In 2020–2021, Mamavation (in partnership with Environmental Health News) commissioned independent laboratory testing of period underwear brands. PFAS — per- and polyfluoroalkyl substances, also called "forever chemicals" — were detected in the crotch panel of multiple brands, including Thinx, which had aggressively marketed itself as a clean, chemical-free product.
PFAS are used to create water- and stain-resistant coatings. They are called "forever chemicals" because they do not break down in the body or the environment. They are associated with thyroid disruption, immune suppression, reduced fertility, developmental toxicity, and cancer. They accumulate in blood, breast milk, and fetal tissue. There is no safe level of PFAS exposure — the EPA's drinking water advisory levels are in parts per trillion.
Thinx settled a class action lawsuit in 2022 for $5 million. The settlement did not require an admission of liability or a product reformulation. Several brands have since removed PFAS-based coatings — but this requires verified third-party testing, not marketing claims. Check Mamavation's updated tested brand list before purchasing (mamavation.com).
Every box of tampons carries a TSS warning. Almost nobody understands the actual mechanism — because explaining it would require explaining what the tampon is made of.
TSS is caused by Staphylococcus aureus bacteria producing TSST-1 (toxic shock syndrome toxin 1) in sufficient quantities to enter the bloodstream and trigger a systemic inflammatory response. The conditions that favor this: warmth, sustained moisture, and a low-oxygen (anaerobic) environment. Superabsorbent synthetic fibers — rayon and its derivatives — create exactly this environment. The more absorbent the tampon, the higher the risk.
The 1980 TSS outbreak that killed at least 38 women and caused 890 documented cases was directly linked to the Rely tampon (Procter & Gamble) — an ultra-absorbent synthetic product that was recalled. The root mechanism has not changed. Modern superabsorbent synthetic tampons create the same favorable conditions. The warning on the box says "use the lowest absorbency for your flow" — it does not explain why, and it does not tell you that the material itself is the variable.
Lower risk alternatives for TSS:
100% organic cotton tampons (no rayon, no synthetic superabsorbent) · Menstrual cups (silicone creates no anaerobic fiber environment) · Menstrual discs · Reusable cloth pads · Organic cotton pads for light days
Polyester, nylon, and spandex underwear are petroleum-derived synthetic textiles. The vulvar and perineal skin is among the thinnest and most absorptive on the body — comparable in permeability to the thin skin behind the ear, which is why nicotine and hormone patches are placed there. Synthetic fabrics in direct contact with this tissue are not inert.
Phthalates in Synthetic Fabric Dyes
Phthalates are used as fixatives in fabric dyes and as plasticizers in synthetic textiles. They are documented endocrine disruptors — interfering with estrogen, progesterone, and testosterone signaling. Studies in women show correlation between urinary phthalate levels and menstrual irregularity, reduced ovarian reserve, and impaired embryo implantation. Phthalates do not bond permanently to fabric — they migrate and off-gas, particularly with body heat and friction.
Heat Trapping & Vaginal Microbiome Disruption
Synthetic fabrics trap heat and moisture in a way that natural fibers do not. Elevated vulvar and vaginal temperature shifts the local microbiome — promoting overgrowth of anaerobic bacteria associated with bacterial vaginosis (BV), which affects approximately 29% of US women. BV is associated with increased STI susceptibility, preterm birth, pelvic inflammatory disease, and fertility challenges. Recurrent BV that doesn't respond to antibiotics may reflect an unaddressed environmental driver.
Azo Dyes in Colored/Patterned Underwear
Azo dyes used in textile coloring can break down into aromatic amines — compounds with documented carcinogenic potential. The EU has restricted 22 aromatic amines in textiles; US regulation lags significantly. Darker colors and more vibrant patterns typically require more chemical treatment. The dyes are not sealed into fiber — they bleed with washing, heat, and sweat, particularly in intimate contact zones.
Male fertility has declined dramatically over the past 50 years. A 2017 meta-analysis (Levine et al., Human Reproduction Update) documented a 59% decline in total sperm count among men in Western countries between 1973 and 2011. The causes are multifactorial — but underwear material is one of the most direct and least discussed variables.
The Scrotal Temperature Problem
The scrotum is anatomically external to the body for a reason: sperm production (spermatogenesis) requires a temperature 2–4°C below core body temperature. The optimal range is 32–36°C. At 37°C (normal body temperature), sperm production slows significantly. At sustained higher temperatures, sperm DNA fragmentation, reduced motility, and morphological abnormalities result.
A study by Shafik (1993, Urology) demonstrated that men who wore polyester underwear for 14 months showed significant reductions in sperm density, motility, and percentage of normal morphology — and that these changes partially reversed after switching to cotton. A follow-up study found scrotal skin temperature was measurably elevated in polyester underwear compared to cotton. This is not a fringe finding — it has been replicated and referenced in fertility research globally.
Phthalates & Testosterone Suppression in Men
Phthalates from synthetic fabrics in direct scrotal contact are absorbed transdermally. Multiple studies have correlated urinary phthalate levels in men with reduced testosterone, reduced sperm quality, and shorter anogenital distance (an indicator of in-utero androgen exposure). Scrotal skin has higher permeability than most skin and produces sweat that can drive phthalate transfer from adjacent fabric.
Tight Synthetic Underwear — Compounded Scrotal Hyperthermia
Tight-fitting synthetic underwear compounds the temperature problem: it holds the scrotum closer to the body (reducing anatomical thermal advantage), traps heat with synthetic insulation, and often contains spandex/elastane which adds further thermally insulating pressure. Studies on laptop heat, heated car seats, and tight clothing all confirm the fertility impact of sustained scrotal temperature elevation above the optimal range.
Spandex & Elastane — Chemical Off-Gassing
Spandex (Lycra/elastane) is polyurethane-based — a petroleum chemical. It requires chemical processing including dimethylformamide (DMF), a liver toxin and suspected reproductive toxicant. Elastane does not biodegrade and sheds microplastic fibers with each wash — which accumulate in water systems and have been detected in human blood, placentas, and breast milk. Even in small quantities, microplastics have been shown to disrupt hormonal signaling and induce oxidative stress.
A healthy vaginal microbiome is dominated by Lactobacillus species — primarily L. crispatus and L. iners. These bacteria produce lactic acid, hydrogen peroxide, and bacteriocins that protect against pathogenic bacteria, yeast overgrowth, sexually transmitted infections, and preterm birth. The vaginal pH maintained by a healthy Lactobacillus community (3.8–4.5) is inhospitable to most pathogens.
What disrupts this ecosystem — and therefore the body's reproductive and systemic immune function:
Recurrent yeast infections, bacterial vaginosis, unusual odor, and unexplained vaginal symptoms are often treated as isolated problems with antifungals and antibiotics. The underlying environmental drivers — fragrance, synthetic fabric, dietary glyphosate load — are rarely addressed. Removing the disruptors is the intervention. It costs nothing and has no side effects.
The bottom line
The products marketed as hygienic are often the source of the problem. The vagina is self-cleaning. The skin of the vulva, scrotum, and perineum does not require synthetic products — it requires air, natural fiber, and the absence of chemicals that override its biology. Every swap in the Action Guide is achievable, affordable, and supported by available research.
What to look for — and what to put back on the shelf.
Avoid These Claims / Ingredients
Choose These Instead
Tampons
Swap conventional cotton-rayon blend for 100% organic cotton, applicator-free or cardboard applicator.
Trusted brands: Natracare (UK standard, widely available), Cora Organic, Rael Organic, LOLA 100% Organic, The Honest Company Organic. Verify the current ingredient list — formulas change.
Pads & Liners
Swap conventional pads for certified organic cotton or reusable cloth pads. Liners especially — these are in contact with vulvar tissue all day, every day.
Trusted brands: Natracare, Cora Organic, Rael Organic. Reusable: GladRags, Lunapads, Imse Vimse — organic cotton or hemp. Hand wash in unscented castile soap; air dry. Lasts years, pennies per use.
Menstrual Cup
Medical-grade silicone, no fiber, no bleach, reusable for up to 10 years. Requires a learning curve (2–3 cycles). Significantly reduces chemical exposure.
Brands: Diva Cup, Lunette, Lena Cup, Saalt. Clean with unscented castile soap between uses; sterilize in boiling water between cycles. Do not use scented cleansers — disrupts vaginal microbiome.
Period Underwear
Only buy brands with verified third-party PFAS-free testing. Marketing claims are not sufficient. Check mamavation.com for the current tested and approved list.
Wash in unscented detergent, cold water, hang dry. Avoid high heat which can off-gas chemical residues from elastics and fabric treatments.
Everyday Underwear — Women
Replace synthetic fabric underwear (polyester, nylon, spandex) with 100% organic cotton, linen, or hemp for the gusset at minimum. Go without when sleeping.
Look for: GOTS certified organic cotton. Avoid anything with a polyester/spandex blend in the crotch panel. Wash in unscented, fragrance-free detergent. A few pairs of true organic cotton underwear cost approximately the same as a pack of conventional synthetic.
Everyday Underwear — Men
Replace tight synthetic underwear with 100% cotton (preferably organic) boxer briefs or traditional boxers. The goal: reduce scrotal temperature, reduce chemical contact, allow airflow.
Research finding: Shafik (1993) documented meaningful sperm quality improvements within months of switching from polyester to cotton. This is one of the most accessible male fertility interventions available — and it costs the same as what you're already buying. Avoid tight waistbands with high elastane content.
Laundry Detergent for Intimate Items
Residual detergent in fabric is in contact with intimate tissue all day. This matters more for underwear than any other clothing item.
Avoid: Any detergent with fragrance, optical brighteners (they deposit on fabric and emit UV), or quaternary ammonium compounds (quats).
Choose: Unscented castile soap (Dr. Bronner's Baby/Unscented), Branch Basics Concentrate (fragrance-free), or washing soda + borax. Rinse twice. Air dry when possible.
| Priority | Change | Why First |
|---|---|---|
| 1 | Switch to organic cotton tampons, unscented | Highest chemical load, most absorptive tissue, most direct systemic exposure |
| 2 | Switch everyday underwear to 100% cotton (both sexes) | Daily all-day contact with thin, absorptive skin; male fertility impact; vaginal microbiome |
| 3 | Eliminate all scented intimate products | Fastest vaginal microbiome restoration; removes fragrance phthalates immediately |
| 4 | Switch to unscented, fragrance-free laundry detergent | All clothing contact; easy, low-cost change |
| 5 | Verify period underwear PFAS-free before next purchase | Don't replace one problem with another |
| 6 | Consider menstrual cup (when ready) | Eliminates fiber exposure entirely; long-term cost savings |
Open
The average woman uses about 11,000 pads or tampons in her lifetime. These products are in direct contact with some of the most absorptive tissue in the human body — tissue that bypasses the liver and sends what it absorbs straight into the bloodstream. And nobody tells her what's in them. Because by federal law, tampon manufacturers don't have to.
Glyphosate
In 2015, Argentine researchers tested 13 brands of cotton-based personal care products — tampons, gauze, cotton balls, swabs. They found glyphosate — the active ingredient in Roundup — in 85% of all samples. Non-organic cotton is one of the most heavily sprayed crops in agriculture, and glyphosate doesn't fully wash out of the fiber. The FDA doesn't require pesticide testing on tampons. The brands did not disclose this. Women were not told. That's what we mean by an informed consent gap.
Dioxins
Most conventional tampons are made of cotton and rayon — both bleached white using chlorine processes. Chlorine bleaching creates dioxins. The FDA says levels are "below detectable limits" and therefore safe. The World Health Organization says dioxins have no safe exposure threshold — they are carcinogenic, immunotoxic, and they accumulate in fat tissue over time. Including ovarian tissue and breast tissue. We are not talking about a single exposure. We are talking about 11,000 exposures through mucous membrane. These are not equivalent conversations.
Toxic Shock Syndrome
Toxic shock syndrome. The box tells you to use the lowest absorbency for your flow and change it every 4–8 hours. What the box doesn't tell you is that TSS is driven by the material itself. Rayon — the synthetic fiber that makes tampons superabsorbent — creates an anaerobic environment that favors the bacteria responsible for TSS. The 1980 outbreak that killed dozens of women was directly linked to an ultra-absorbent synthetic tampon. The mechanism hasn't changed. Just the marketing.
Period Underwear
Then came period underwear — marketed as the clean, chemical-free alternative. In 2020 and 2021, independent testing commissioned by Mamavation found PFAS — forever chemicals — in the crotch panel of multiple brands, including Thinx. PFAS are associated with thyroid disruption, cancer, immune suppression, and infertility. Thinx settled a $5 million class action. The lesson: "clean" on a label requires third-party verification, not marketing copy.
Synthetic Underwear
And this isn't only a women's issue. For men, synthetic underwear is a fertility variable that almost nobody discusses. The scrotum is external to the body for a specific reason: sperm production requires a temperature 2 to 4 degrees cooler than core body temperature. Polyester underwear traps heat, raises scrotal temperature, and has been shown in controlled studies — including a 1993 study published in Urology — to reduce sperm density, motility, and normal morphology after sustained wear. The effects partially reversed when men switched to cotton. Beyond heat, synthetic fabrics off-gas phthalates — endocrine-disrupting compounds that suppress testosterone and have been correlated in multiple studies with reduced sperm quality and shorter anogenital distance. This is a documented mechanism. It costs nothing to change. Nobody tells men about it.
Vaginal Microbiome
For women, the downstream effect includes vaginal microbiome disruption. A healthy vaginal microbiome is dominated by Lactobacillus bacteria — which protect against infection, support fertility, and reduce preterm birth risk. Synthetic fabric, fragranced products, and glyphosate-containing tampons all suppress these protective bacteria. Recurrent BV, yeast infections, and unexplained symptoms are often treated with antibiotics and antifungals — without ever addressing what's causing the disruption in the first place.
Close
The swaps are simple, mostly affordable, and they're in the Action Guide tab. Organic cotton tampons. Cotton underwear. PFAS-verified period underwear. Unscented everything. The vagina is self-cleaning. The vulva and scrotum are not asking for synthetic chemicals, dyes, or herbicide residues. They're asking to be left alone by industrial chemistry — and that turns out to be surprisingly easy once you know what to look for.
Glyphosate in Cotton Products — SENASA Argentina (2015)
Mañas F et al. Commissioned by Argentina's national food and drug authority. Tested 13 brands. Found glyphosate and/or AMPA in 85% of samples including tampons, cotton balls, gauze, and swabs. Results presented at Argentine Congress of Toxicology, 2015. Search: "Mañas glyphosate cotton tampons 2015."
PFAS in Period Underwear — Mamavation / Environmental Health News (2020–2021)
Independent lab testing commissioned by Mamavation found PFAS in multiple period underwear brands including Thinx, Knix, and others. Updated list of tested brands (pass/fail) at mamavation.com. Thinx class action settlement 2022: $5 million.
Synthetic Underwear & Male Fertility — Shafik A. (1993)
Shafik A. "Effect of different types of textile fabric on spermatogenesis: an experimental study." Urology, 1993;41(5):532-6. Men wearing polyester underwear for 14 months showed significant reductions in sperm density, motility, and morphology. Partially reversed after switching to cotton.
Western Sperm Count Decline — Levine et al. (2017)
Levine H et al. "Temporal trends in sperm count: a systematic review and meta-regression analysis." Human Reproduction Update, 2017;23(6):646–659. 59% decline in total sperm count in Western men from 1973 to 2011. No comparable decline in non-Western populations studied.
Dioxins & Human Health — WHO Fact Sheet
WHO Fact Sheet: Dioxins and their effects on human health. Classifies dioxins as highly toxic, carcinogenic, immunotoxic, reproductively toxic. States there is no known safe threshold of exposure. Available at who.int.
Phthalates & Female Reproductive Health
Hauser R et al. "Urinary phthalate metabolites and outcomes of in vitro fertilization." Environmental Health Perspectives, 2016. Higher phthalate levels associated with lower fertilization rates and fewer top-quality embryos. Multiple subsequent studies confirm association with menstrual irregularity and reduced ovarian reserve.
Toxic Shock Syndrome & Tampon Absorbency
Chesney PJ et al. "The disease spectrum, epidemiology, and etiology of toxic-shock syndrome." Annual Review of Microbiology, 1984. Bergdoll MS. "Staphylococcal toxins and toxic shock syndrome." Journal of Food Safety, 1984. Historical documentation of the Rely tampon recall and rayon-TSS mechanism.
Vaginal Microbiome & Systemic Health
Ravel J et al. "Vaginal microbiome of reproductive-age women." PNAS, 2011. The foundational characterization of healthy Lactobacillus-dominated vaginal flora. Fettweis JM et al. "The vaginal microbiome and preterm birth." Nature Medicine, 2019. BV and Lactobacillus depletion as preterm birth risk factor.
Mamavation
mamavation.com — PFAS testing results for period underwear, personal care, food packaging. The most consistently updated independent testing resource for consumer products.
EWG Skin Deep Database
ewg.org/skindeep — Ingredient hazard ratings for personal care products. Useful for evaluating intimate washes, lubricants, and cycle-care products by ingredient.
GOTS Certification
global-standard.org — Global Organic Textile Standard. The most rigorous organic certification for textiles including underwear and period products. Look for the GOTS logo, not just "organic cotton" claims.
FDA Tampon Q&A
fda.gov — Search "tampon safety." Useful for understanding what is and is not required to be disclosed — and the gap between "below detectable limits" and "safe." Read critically.