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Is Plastic Clothing Lowering Your Testosterone? What the Science Actually Says

Polyester underwear, BPA in socks, microplastics in testicles: we read the actual studies. Here's what's well established, what's still a hunch, and what you can sensibly do about it.

By Peter Martin · Published

You’ve probably seen the claim somewhere: a podcast clip, a viral post, a friend at the pub. Men’s testosterone is crashing, sperm counts are halving, and the plastic in our clothes is to blame. Polyester boxers, stretchy gym leggings, synthetic socks. All of it, supposedly, quietly messing with our hormones.

It’s a compelling story, and parts of it are true. Some chemicals used in plastics really do interfere with hormones. Sperm counts really have been reported to fall. And yes, researchers have found hormone-disrupting chemicals in ordinary clothes.

But “parts of it are true” isn’t the same as “it’s proven.” We went back to the original studies, including the famous “polyester underwear” experiments that get passed around online, to see what they actually found. Here’s the honest picture.

Two findings sit behind most of the headlines.

Sperm counts. The biggest analysis to date, led by Hagai Levine and Shanna Swan, pooled 223 studies with semen samples collected between 1973 and 2018. Among men not selected for fertility, average sperm concentration fell by 51.6% over that period, and the yearly rate of decline appeared to speed up after 2000.1 That’s a striking result from a serious team. But notice what the authors say at the end: research on the causes of the decline is “urgently needed.” In other words, the study shows a trend. It doesn’t tell us what’s driving it.

Testosterone. In a long-running study of randomly selected men aged 45 to 79 in the Boston area, Thomas Travison and colleagues found a “substantial, age-independent” fall in testosterone levels between the late 1980s and early 2000s. Smoking and obesity didn’t explain it.2 The authors suggested it could be due to differences between generations or to “health or environmental effects not captured” in their data. Again, it’s a real signal, but from one cohort, and the cause is open.

So when someone says “plastics are why testosterone is falling,” they’re joining two dots that science hasn’t yet joined. Plastics are one suspect. Weight, sleep, activity, diet, how and when blood is measured, and other chemicals are all on the list too.

Part 2: Some plastic chemicals really are hormone disruptors

This is the most solid part of the story.

The US National Institute of Environmental Health Sciences (NIEHS) describes endocrine disruptors as chemicals that can interfere with the body’s hormone system. Its list of common ones includes bisphenol A (BPA), used in some plastics and resins; phthalates, used as plasticizers in hundreds of products; and PFAS, the “forever chemicals” used in non-stick and stain-repellent coatings. The NIEHS specifically names textile coatings as one use of PFAS.3 The Endocrine Society, a leading professional body for hormone specialists, published a scientific statement of about 150 pages in 2015 reviewing the evidence on these and other chemicals, including their effects on male and female reproductive health, and treated endocrine-disrupting chemicals as a real public-health concern.4

Phthalates and testosterone. The best-known human study here used US national survey data (NHANES 2011–2012). Researchers measured phthalate breakdown products in urine and testosterone in blood. In boys aged 6 to 12, higher levels of one common phthalate (DEHP) were linked to 29% lower testosterone. In adult men, the links showed up mainly in men aged 40 to 60.5 That’s a meaningful finding. It’s also a snapshot taken at a single point in time, so it shows an association, not proof that phthalates caused the lower levels. And the phthalates in those men came from all sources: food packaging, personal care products and more, not specifically clothes.

BPA, by the regulator’s numbers. In 2023, the European Food Safety Authority (EFSA) cut its safe daily intake for BPA from 4 micrograms to 0.2 nanograms per kilo of body weight. That’s a 20,000-fold reduction. EFSA also concluded that average dietary exposure in Europe exceeds that new limit by two to three orders of magnitude, which it called “a health concern.”6 One detail is worth knowing: the effect EFSA based its limit on was on the immune system, not testosterone. And its assessment was about BPA in food, the exposure route regulators focus on most.

So: plastic chemicals can disrupt hormones. That part is well supported. The next question is whether your clothes are a meaningful source.

Part 3: Yes, these chemicals turn up in clothes

BPA in socks. In 2017, scientists at the New York State Department of Health tested 77 textile and infant clothing samples. BPA was found in 82% of them. Socks had by far the highest levels, an average of 1,810 nanograms per gram, and the single highest reading, 13,300 ng/g, came from a 97% polyester fabric marketed for babies.7

A Spanish team then tested 32 pairs of children’s socks and found BPA in about 91% of samples. Extracts from some socks showed hormone-like activity in lab cell tests, and BPA appeared to contribute to it.8 Here’s the twist, though: in that study, BPA levels were about 25 times higher in socks from the store whose socks had more cotton in them. Cotton isn’t automatically chemical-free. Dyes, prints and finishes matter.

In the US, the Center for Environmental Health, a nonprofit, said in 2022 that it had sent California Proposition 65 legal notices to around 100 companies, covering more than 100 sock brands, over BPA in socks. It found BPA in socks made mainly of polyester with spandex, and said it had not found BPA in socks made mainly of cotton.9 That’s a legal action based on the group’s own testing, not a peer-reviewed study, but it points the same way.

PFAS in “stain-resistant” clothes. A 2022 study tested 72 children’s products sold as stain-resistant in the US and Canada, mostly school uniforms. PFAS turned up in every single one.10 And here’s the most important finding for anyone who thinks “just buy cotton” solves everything: the 100% cotton uniforms contained higher PFAS levels than the synthetic blends. The chemicals came from the stain-repellent finish, not the fiber.

So the real lesson isn’t simply “plastic fiber bad, cotton good.” It’s that chemical finishes and plastic-based fibers are both ways these substances get into clothes.

Part 4: Does it actually get into you?

Finding a chemical in a sock isn’t the same as finding it in your bloodstream. This is where the evidence gets thinner.

  • Estimated doses are small. Neither sock study measured anything in people. They estimated how much might pass through skin. The Spanish team’s estimate for children was a median of 17.6 picograms per kilo per day,8 a tiny fraction of EFSA’s limit. The New York team’s worst case for infants was up to 7,280 picograms (7.28 nanograms) per kilo per day.7 That worst case is above EFSA’s dietary limit, but it’s a modeled estimate for babies, and EFSA’s figure is for food eaten, not skin contact. Fair summary: clothing is a plausible extra source worth reducing, not a proven cause of harm.
  • Some PFAS can cross skin, at least in the lab. Using lab-grown 3D human skin models, a 2024 study found that short-chain PFAS were absorbed in substantial amounts, while long-chain ones mostly stayed in the skin.11 The chemicals were applied directly in a solvent, not via fabric, so real-world clothing exposure is still unknown.
  • Microplastic particles mostly don’t get through healthy skin. A 2025 review of 46 studies on skin exposure found particles mostly stayed in the outer layer of skin and in hair follicles. The authors concluded the evidence does “not demonstrate systemic availability” of intact micro- and nanoplastics through healthy, intact skin.12 Very small particles and damaged skin are still open questions.

Part 5: Microplastics in testicles: what that study does and doesn’t show

In 2024, a University of New Mexico team made headlines by finding microplastics in all 23 human testes and all 47 dog testes they tested. In the dogs, levels of certain plastics (PVC and PET) were linked to lower testis weight.13 It’s an important and genuinely unsettling finding.

But it’s a study about presence, not cause. It doesn’t show where those plastics came from, and it doesn’t link them to testosterone in people. Most microplastic exposure is thought to come from what we eat, drink and breathe.12 Clothing does shed fibers into the air and the wash, so it’s part of the wider microplastic problem. But no study has yet linked microplastics from clothing to hormone levels.

Speaking of shedding: a Plymouth University study estimated that a single 6 kg wash of acrylic fabric could release over 700,000 fibers. Polyester-cotton blends shed significantly fewer fibers than pure polyester or acrylic.14 Cotton sheds fibers too. A North Carolina State study (co-authored by researchers from Cotton Incorporated, an industry body, which is worth knowing) found cotton and rayon actually shed more fiber by weight than polyester in the lab. The difference is what happens next: in their water tests, cotton fibers broke down, while polyester fibers are expected to persist for a long time.15

Part 6: The “polyester underwear” studies everyone shares

If you’ve read anything about plastic clothing and male hormones, you’ve probably seen a version of: “A study found polyester underwear made men infertile.” It’s based on real research by Egyptian surgeon Ahmed Shafik in the early 1990s. Here’s what those studies actually did.

The 1992 study (the one about sperm). Fourteen men wore a polyester scrotal sling, a tight pouch, not ordinary underwear, day and night for 12 months. All 14 stopped producing sperm, after an average of about 140 days. Sperm production returned after they stopped wearing it.16 Shafik thought the cause was static electricity from the fabric rubbing against skin, plus changes in temperature. Crucially for the testosterone question: “Serum reproductive hormones showed no significant change.” The study people cite as proof that polyester lowers testosterone found hormone levels didn’t change.

The rat and sex-drive studies. Shafik also put rats in polyester, poly-cotton, cotton or wool pants for up to a year, and reported less sexual activity in the polyester groups, which recovered after the pants came off.17 He reported a similar result in a study of 50 men.18

How much weight to give them? These were small studies from a single researcher, using unusual set-ups (the sling especially), and as far as we can find they’ve never been independently repeated. They’re interesting, and they’re worth telling honestly. They’re not strong enough to say polyester underwear lowers your testosterone.

What does have better evidence: fit and heat. A 2018 Harvard study of 656 men at a fertility clinic found that men who mostly wore boxers had 25% higher sperm concentration than men who wore tighter styles.19 The explanation is likely heat. Testicles work best a little cooler than the rest of the body. It’s still an observational study, and it’s about sperm, not testosterone. The researchers didn’t find a link with testosterone, though they note their blood timing may have missed one. It’s also about fit, not fabric.

So what’s the honest bottom line?

Here’s how we’d grade each claim:

Claim How strong is the evidence?
Some plastic chemicals (BPA, phthalates, some PFAS) disrupt hormones Strong. Recognized by NIEHS, the Endocrine Society and EU regulators
Sperm counts have fallen since the 1970s Strong as a reported trend. The cause is unknown
Higher phthalate levels go with lower testosterone Moderate. Consistent associations, not proof of cause
BPA and PFAS are found in clothing Strong. Measured in multiple studies
Chemicals in clothes reach your bloodstream in meaningful amounts Weak / unknown. Lab and modeled estimates only
Microplastics from clothing get through healthy skin Not supported by current evidence
Polyester underwear lowers testosterone Not supported. The key study found no hormone change
Tight underwear can affect sperm Moderate. About heat and fit, not fiber
Switching to cotton raises testosterone No evidence. No study has tested this

That last line matters. We’re a site about 100% cotton, and we’d love to tell you cotton boosts testosterone. It doesn’t, as far as anyone knows, and we won’t pretend otherwise.

What the evidence does support is a simpler idea: you’re exposed to hormone-disrupting chemicals from many directions, and it’s sensible to cut the avoidable ones. Clothing is one of the easier ones to control.

What you can practically do

None of this needs to be expensive or obsessive. In rough order of impact:

  1. Start with food, not your wardrobe. EFSA’s biggest concern about BPA is what we eat.6 Common-sense steps are to avoid microwaving food in plastic, choose glass or steel containers for hot food, and eat more fresh food and less packaged food. This probably matters more than anything in your drawer.
  2. Talk to your doctor if you have symptoms. Low testosterone is diagnosed with blood tests, and things like sleep, weight, alcohol and some medicines have well-established effects.
  3. Choose looser underwear if fertility is a concern. The best evidence on underwear is about heat and fit.19
  4. Skip “stain-resistant,” “water-repellent” and “wrinkle-free” finishes, especially for kids’ clothes and things worn all day. That’s where PFAS showed up, even on cotton.10
  5. Look at socks and underwear first. They sit against your skin all day, and socks had the highest BPA levels in testing.7 Plain, undyed or lightly dyed cotton is a sensible swap.
  6. Prefer certified organic cotton. GOTS bans PFAS and restricts chemical inputs during processing. OEKO-TEX STANDARD 100 tests finished products for harmful substances. Neither one guarantees a product is 100% cotton, though. Our guide to GOTS vs OEKO-TEX vs OCS explains what each label really covers.
  7. Check the parts the label skips. A “100% cotton” label can legally ignore polyester sewing thread and a spandex or rubber waistband. How to Tell if Sheets Are Really 100% Cotton shows you what to look for, and the same checks apply to clothing.
  8. Wash new clothes before wearing them. It’s a common-sense step to remove some of the leftover finishing chemicals and dyes. We haven’t found a study measuring how much BPA or PFAS one wash removes, so treat it as a sensible habit, not a fix.

Can you actually find socks and underwear that are cotton all the way through? Yes, but they’re rare, because almost everything stretchy relies on elastane, nylon or rubber. One example we’ve checked is Cottonique’s Elite Elastic-Free socks. Cottonique says they contain no spandex, latex, polyester or nylon, and no polyester sewing thread in the toe seam. They stretch through the way they’re knitted instead. We’re putting together full, verified roundups of elastic-free cotton underwear and socks next, with the thread, waistband and buttons of every pick checked. This isn’t an affiliate link, and we haven’t been paid to mention it.

The takeaway

The fear version of this story, “your polyester boxers are draining your testosterone,” isn’t backed by the evidence, and the study most often quoted actually found hormone levels didn’t change. The calmer version holds up much better. Hormone-disrupting chemicals are real, they’re in more products than most people realize, including some clothes, and cutting the avoidable sources is a reasonable choice. Plain, untreated, genuinely 100% cotton is one easy way to do that. It just won’t do the job of a doctor, a decent diet or a good night’s sleep.

Frequently asked questions

Does polyester underwear lower testosterone?

There is no good evidence that it does. The study most often cited (Shafik, 1992) had 14 men wear a polyester scrotal sling, not ordinary underwear, for a year. Their sperm production stopped and later recovered, but their reproductive hormone levels showed no significant change. The study has not been independently replicated.

Do plastics lower testosterone?

Some plastic-related chemicals, especially phthalates, are linked to lower testosterone in human studies, but those studies show associations at one point in time rather than proof of cause. Most exposure comes from food, packaging and personal care products rather than clothing.

Is there BPA in clothes?

Yes. A 2017 study found BPA in 82% of 77 textile and infant clothing samples, with the highest levels in socks, especially a 97% polyester infant fabric. A 2019 Spanish study found BPA in about 91% of children's sock samples. How much passes through skin into the body is still uncertain.

Is cotton clothing free of harmful chemicals?

Not automatically. A 2022 study of stain-resistant school uniforms found higher PFAS levels in 100% cotton uniforms than in synthetic blends, because the chemicals came from the stain-repellent finish. Untreated cotton, ideally GOTS certified, is the better choice.

Will switching to cotton raise my testosterone?

No study has shown that. Choosing untreated cotton is a reasonable way to reduce one possible source of chemical exposure, but if you are worried about low testosterone, see a doctor for a blood test, because sleep, weight, alcohol, medicines and medical conditions have much better-established effects.

Can microplastics from clothes get into my body through my skin?

Current evidence says intact microplastic particles mostly stay in the outer layer of healthy skin. A 2025 review of 46 studies found no demonstration that they enter the body through healthy, intact skin, though very small particles and damaged skin are still being studied.

Sources

Footnotes

  1. Levine H, Jørgensen N, Martino-Andrade A, et al. Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries. Human Reproduction Update. 2023;29(2):157–176. ↩

  2. Travison TG, Araujo AB, O’Donnell AB, et al. A population-level decline in serum testosterone levels in American men. Journal of Clinical Endocrinology & Metabolism. 2007;92(1):196–202. ↩

  3. National Institute of Environmental Health Sciences, Endocrine Disruptors. ↩

  4. Gore AC, Chappell VA, Fenton SE, et al. EDC-2: The Endocrine Society’s second scientific statement on endocrine-disrupting chemicals. Endocrine Reviews. 2015;36(6):E1–E150. ↩

  5. Meeker JD, Ferguson KK. Urinary phthalate metabolites are associated with decreased serum testosterone in men, women, and children from NHANES 2011–2012. Journal of Clinical Endocrinology & Metabolism. 2014;99(11):4346–4352. ↩

  6. EFSA Panel on Food Contact Materials, Enzymes and Processing Aids. Re-evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs. EFSA Journal. 2023;21(4):e06857. ↩ ↩2

  7. Xue J, Liu W, Kannan K. Bisphenols, benzophenones, and bisphenol A diglycidyl ethers in textiles and infant clothing. Environmental Science & Technology. 2017;51(9):5279–5286. ↩ ↩2 ↩3

  8. Freire C, Molina-Molina JM, Iribarne-Durán LM, et al. Concentrations of bisphenol A and parabens in socks for infants and young children in Spain and their hormone-like activities. Environment International. 2019;127:592–600. ↩ ↩2

  9. Center for Environmental Health, CEH Finds 100+ Sock Brands with High Levels of BPA (December 16, 2022). ↩

  10. Xia C, Diamond ML, Peaslee GF, et al. Per- and polyfluoroalkyl substances in North American school uniforms. Environmental Science & Technology. 2022;56(19):13845–13857. ↩ ↩2

  11. Ragnarsdóttir O, Abou-Elwafa Abdallah M, Harrad S. Dermal bioavailability of perfluoroalkyl substances using in vitro 3D human skin equivalent models. Environment International. 2024;188:108772. ↩

  12. McLean P, Christopher EA, Sleeuwenhoek A, et al. Dermal exposure, review of current knowledge on the uptake of micro- and nano-plastics. Microplastics and Nanoplastics. 2025;6. ↩ ↩2

  13. Hu CJ, Garcia MA, Nihart A, et al. Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis. Toxicological Sciences. 2024;200(2):235–240. ↩

  14. Napper IE, Thompson RC. Release of synthetic microplastic plastic fibres from domestic washing machines: effects of fabric type and washing conditions. Marine Pollution Bulletin. 2016;112(1–2):39–45. ↩

  15. Zambrano MC, Pawlak JJ, Daystar J, et al. Microfibers generated from the laundering of cotton, rayon and polyester based fabrics and their aquatic biodegradation. Marine Pollution Bulletin. 2019;142:394–407. ↩

  16. Shafik A. Contraceptive efficacy of polyester-induced azoospermia in normal men. Contraception. 1992;45(5):439–451. doi:10.1016/0010-7824(92)90157-O. ↩

  17. Shafik A. Effect of different types of textiles on sexual activity (rat study). European Urology. 1993;24(3):375–380. ↩

  18. Shafik A. Effect of different types of textiles on male sexual activity. Archives of Andrology. 1996;37(2):111–115. ↩

  19. Mínguez-Alarcón L, Gaskins AJ, Chiu YH, et al. Type of underwear worn and markers of testicular function among men attending a fertility center. Human Reproduction. 2018;33(9):1749–1756. ↩ ↩2

Facts in this article were last checked on October 20, 2026. Spotted something out of date? Tell us; we correct errors and note the change.

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