Is Polyester Bad for You? The Fabric Is Inert. The Finish Isn’t.

What is polyester, and why isn’t the fabric itself the worry?

Nearly all clothing polyester is polyethylene terephthalate, or PET. It is the same polymer as a soda bottle, spun into fibre instead of blown into a bottle. As a solid it is hard to digest, hard to dissolve and hard to break down chemically. In one 13-week feeding study, rats ate ground PET and polyethylene fabric at up to 5% of their diet, and the researchers found no toxicologically relevant effects and no mutagenicity. That study was run by Altria, which used the fabric in oral pouches, so treat it as a floor rather than the final word. Germany’s Federal Institute for Risk Assessment (BfR) reaches the same practical conclusion: genuine allergy to textiles is relatively rare, and the problems it does see come from chemicals applied to the fibre.

So “is polyester bad for you?” is really five smaller questions, and they have different answers. If you only want to know whether polyester counts as plastic, it does; see is polyester plastic, and when it sheds most. This page is about the person wearing it.

Does polyester activewear contain BPA?

Some does. Between 2022 and 2023 the Center for Environmental Health (CEH), a California nonprofit, sent legal notices under the state’s Proposition 65 law. CEH said its testing of sports bras, leggings, shorts and athletic shirts “made primarily of polyester with spandex” found BPA exposures up to 22 times California’s safe-harbour limit in 2022, and up to 40 times in 2023. That limit is 3 micrograms per day for skin contact. The resulting lawsuit, CEH v. Athleta LLC in San Francisco Superior Court, names about 40 companies, including Nike, Patagonia, Adidas, Target and Walmart. Athleta told CNN it believed the claims had “no merit”. These are allegations, and CEH has not published the measurements behind them.

One piece of the case has concluded. David Peyser Sportswear, one of the defendants over polyester-spandex leggings, settled. A corrected consent judgment dated 10 February 2026 requires its leggings sold in California to contain no more than 50 parts per billion BPA. It also restricts swapping in other bisphenols such as BPS and BPF. A settlement is not a court ruling on the science, and the rest of the case remains open.

Peer-reviewed studies agree that BPA turns up in clothes: in 82% of 77 textiles in one New York study, and in every used garment in another, where it also transferred between clothes in the wash. But in Spanish infant socks, the cotton-rich samples had more BPA. It comes from dyeing and finishing, not the polyester molecule. And nobody has measured how much reaches a wearer. Every skin dose is modelled; the closest human evidence is thermal receipts, where BPA kept appearing in urine for days after five minutes of handling.

What about antimony in polyester?

Antimony trioxide is the catalyst used to make PET, so traces stay in almost all polyester: about 87–147 mg/kg on average in a German survey of 433 garments. Only 0.05–2% came out into artificial sweat in a 2021 study, most of it in the first wash-out, so washing new clothes once helps. Danish EPA modelling put wearing polyester at roughly 1% of the WHO tolerable intake, and 41 of 42 Florida firefighters in antimony-treated trousers had normal urine levels. IARC rates trivalent antimony as probably carcinogenic, mainly from workplace exposure. For a wardrobe, it is the lowest priority here.

Why does polyester make some people itch?

Usually the culprit is the dye. Polyester can’t take the water-soluble dyes used on cotton, so it is coloured with disperse dyes, small molecules that dissolve into the fibre. Some of them are well-established skin allergens, and they can leach with sweat, especially from dark, tight garments. In an Ottawa clinic study of 788 patients, 40 reacted to textile dyes. Most reacted to Disperse Blue 106 (33 of 40) or Disperse Blue 124 (32 of 40). Of the patients who were also tested with their own clothes, nine reacted to blue or black linings made of 100% acetate or polyester.

Across European and US clinics, 2.1–6.9% of patients referred for dermatitis reacted to a textile dye mix, and people allergic to hair dye (PPD) react more often. If a rash tracks a waistband or dark lining, ask for the textile dye series; a standard patch test may miss it. Polyester also traps sweat and odour bacteria: after a spin class, polyester shirts smelled significantly worse than cotton.

Is there PFAS in polyester clothing?

Only if it has been finished with it, and cotton can be finished the same way. A 2022 study of 72 stain-resistant children’s products, mostly school uniforms, found that uniforms made of 100% cotton had higher PFAS than synthetic blends. The chemistry comes from the stain- or water-repellent treatment, not the fibre. California (from 2025) and New York (from the end of 2023) ban intentionally added PFAS in apparel. Elsewhere, watch for “stain-resistant”, “water-repellent” and “DWR” on everyday clothes.

Is spandex toxic? And what about nylon?

Spandex (elastane, Lycra) is a polyurethane, the stretchy minority of activewear blends. CEH never said whether the BPA came from the spandex or the polyester. Spandex’s own issue is solvent residue such as DMAc, which OEKO-TEX caps at 0.10% in elastane. Nylon raises the same additive questions; in a lab study of airway organoids, inhaled nylon fibres did more harm than polyester, through chemicals leaching from the nylon. That is a cell test, not a reason to bin your leggings.

Do you breathe in polyester fibres?

A little. Wearing clothes sheds fibres into the air on a similar scale to washing them. In three apartments, a breathing mannequin inhaled up to 272 microplastic particles a day at the worst spot; polyester was 81% of the synthetic ones, but synthetics were only about 4% of everything inhaled. PET made up 18% of plastic particles in a 2022 lung-tissue study. Many indoor fibres are too large to go deep, so swallowed dust matters more, especially for toddlers. See microplastics in the air you breathe.

Can polyester underwear affect fertility?

The claim traces to a 1992 study in which 14 men wore a polyester scrotal sling day and night for a year as a contraceptive. All temporarily stopped producing sperm and recovered afterwards. It tested a sling, not underwear, and has never been replicated. Better evidence points at heat and fit: among 656 men at a Boston fertility centre, boxer wearers had 25% higher sperm concentration, with fabric not recorded. And in 2024 human testes, polyethylene dominated while PET ranked ninth of 12 plastics. More in synthetic underwear and male fertility.

What actually lowers your exposure

1. Wash new synthetics before first wear. It removes the most soluble antimony, dye and finish residue.
2. Change out of sweaty activewear soon after training. Sweat and long skin contact drive the modelled BPA dose.
3. Skip stain- and water-repellent finishes on everyday clothes, especially uniforms and children’s clothes.
4. Get patch-tested for a rash that follows your clothes, and ask for the textile dye series.
5. Choose loose underwear if fertility is the concern. Fit has better evidence than fibre.
6. Treat OEKO-TEX as a screen, not a BPA-free guarantee, and keep household dust down.

Related: how polyester sheds in the wash, in how much microplastic your laundry releases; the wider microfibre problem in clothing; and why “BPA-free” claims deserve a second look, in is BPA-free plastic safe?