Polyester, the most widely produced synthetic fiber in the world, interacts with your body through several pathways: chemicals leaching into sweat, dyes triggering skin reactions, bacteria thriving on the fabric’s surface, and microfibers shedding into your environment. Most of these exposures are low-level, and for many people they never produce obvious symptoms. But the cumulative picture is more complex than “just a fabric,” and the science on some fronts is still catching up.
Antimony Leaching Through Sweat
Polyester is made from polyethylene terephthalate (PET), and its manufacturing process typically relies on antimony trioxide as a catalyst. That means trace amounts of antimony remain embedded in the finished fibers. When you sweat, some of that antimony dissolves and migrates onto your skin. One study measured antimony concentrations in polyester textiles ranging from roughly 125 to 470 micrograms per gram and found that between about 0.05 and 2 percent of the total antimony leached into artificial sweat solutions.1PubMed. Antimony release from polyester textiles by artificial sweat solutions: A call for a standardized procedure
Whether those amounts are enough to matter depends on how much polyester you wear and for how long. A separate risk assessment found that antimony showed the highest mean hazard quotient among the trace elements migrating from skin-contact clothing. For one polyester T-shirt tested, the hazard quotient exceeded the safety threshold, leading the researchers to flag potential health risks for people who wear polyester frequently and for extended periods.2Textile Research Journal. Trace elements in skin-contact clothes and migration to artificial sweat: Risk assessment of human dermal exposure That does not mean a single polyester shirt is dangerous. It means that if polyester dominates your wardrobe and you sweat heavily in it day after day, the cumulative antimony exposure is worth being aware of, particularly because antimony is classified as a possible carcinogen by some regulatory bodies.
Dyes and Contact Dermatitis
If you have ever developed an itchy rash in areas where clothing fits snugly, the fabric itself might not be the culprit so much as the dyes bonded to it. Polyester is typically colored with disperse dyes, a class of colorants that do not dissolve in water and instead adhere to the fiber’s surface. These dyes are considered among the most important allergens in textile dermatitis.3PubMed. Contact allergy from disperse dyes in textiles: a review Sweat, heat, and friction help release dye molecules from the fabric, and people who are sensitized can develop allergic contact dermatitis in the spots where fabric presses closest to skin: the inner thighs, waistband area, armpits, and neck.
Not everyone reacts. Allergic contact dermatitis requires prior sensitization, meaning your immune system has to encounter the dye and decide it is a threat before a rash develops on subsequent exposures. But because polyester relies on disperse dyes more than most other fabrics do, it is disproportionately represented in textile allergy cases. If you suspect a clothing-related rash, a dermatologist can patch-test you against common disperse dyes to confirm or rule it out.
Azo Dyes and Hidden Aromatic Amines
Beyond allergic reactions, a deeper concern involves azo dyes, the single largest class of textile colorants. Bacteria that naturally live on your skin can break down certain azo dyes, releasing aromatic amines that may then be absorbed through the skin.4PubMed. Azo dyes in clothing textiles can be cleaved into a series of mutagenic aromatic amines which are not regulated yet Some of these aromatic amines are mutagenic, meaning they can damage DNA in lab tests. Regulations in the EU and elsewhere already ban a list of specific azo dyes known to release carcinogenic amines, but the research suggests that additional mutagenic amines not yet covered by regulation can also be liberated from legal dyes. This is an area where the regulatory framework has not fully caught up to the chemistry.
Phthalates as Plasticizers
Phthalate esters show up in clothing because they are used as plasticizers to improve the flexibility and durability of synthetic materials, including printed designs, coatings, and certain finishes applied to polyester fabrics. The concern with phthalates is that they are not chemically locked into the material. They can migrate out over time, especially with heat and moisture. Once on your skin, they can be absorbed. Phthalates are associated with endocrine disruption, meaning they can interfere with hormone signaling, and some have been linked to reproductive toxicity in animal and human studies.5PubMed Central. Phthalate esters in clothing: A review
The dose you absorb from a single garment on a single day is tiny. But clothing sits against your skin for hours at a stretch, and if you combine that with phthalate exposure from food packaging, cosmetics, and household products, the total load adds up. Children and pregnant women are typically considered the most vulnerable populations for phthalate effects because of the timing of hormonal and developmental processes.
Flame Retardants and Water-Repellent Finishes
Polyester garments, especially those marketed for outdoor performance or treated for water resistance, sometimes carry additional chemical finishes. Chlorinated organophosphate flame retardants are one category found in treated fabrics. Research using lab-grown human skin equivalents showed that three common chlorinated flame retardants were dermally bioavailable at rates between roughly 3.5 and 26 percent of the exposure dose after 24 hours of contact with furniture fabrics.6PubMed. Dermal uptake of chlorinated organophosphate flame retardants via contact with furniture fabrics; implications for human exposure That study focused on furniture textiles rather than clothing, but the mechanism is the same: skin contact transfers the chemicals.
Water-repellent treatments on outdoor and activewear often involve per- and polyfluoroalkyl substances (PFAS), sometimes called “forever chemicals” because they break down extremely slowly in the environment and in the body. A review examining dermal uptake of PFAS highlighted that this exposure route has received far less research attention than ingestion or inhalation, meaning the risk from wearing PFAS-treated clothing is not well quantified yet.7PubMed Central. Dermal uptake: An important pathway of human exposure to perfluoroalkyl substances? The honest assessment is that scientists know PFAS transfers to skin from treated textiles, but do not yet have enough data to say how much harm typical clothing exposure causes.
Why Polyester Smells Worse After a Workout
If you have ever noticed that your synthetic gym shirt develops a powerful odor that cotton never seems to match, you are not imagining it. The reason is bacterial. After a fitness session, researchers found that polyester shirts selectively enriched a group of bacteria called Micrococci, which were present on almost all synthetic shirts tested and were detected almost exclusively on synthetic rather than cotton fabric.8PubMed Central. Microbial odor profile of polyester and cotton clothes after a fitness session Micrococci are especially efficient at converting sweat compounds into the volatile molecules we perceive as body odor.
This happens because polyester’s smooth, hydrophobic surface does not absorb moisture the way cotton fibers do. Sweat sits on the surface, creating a warm, moist film that certain odor-producing bacteria colonize more readily than others. Cotton, by contrast, absorbs moisture into its fibers and supports a different bacterial community that tends to produce less pungent byproducts. The practical upshot: polyester activewear needs to be washed promptly and thoroughly after sweating, and even then, some people find odors become embedded over time in ways that laundering cannot fully reverse.
There is also a broader dimension to consider. The relationship between your skin’s natural microbiome and the textile microbiome is increasingly recognized as a two-way street. Antimicrobial finishes applied to polyester to combat odor can themselves disrupt your skin’s normal bacterial ecosystem, potentially doing more harm than good in some cases.9PubMed Central. The Future of Functional Clothing for an Improved Skin and Textile Microbiome Relationship
Thermoregulation and Comfort
A common belief is that polyester traps heat and makes you hotter than natural fibers. The research is surprisingly ambiguous on this. A narrative review of studies comparing natural and synthetic fabrics during exercise found that few studies identified significant differences in body temperature, perceived comfort, or performance between the two categories.10PubMed Central. The Role of Sports Clothing in Thermoregulation, Comfort, and Performance During Exercise in the Heat: A Narrative Review The studies covered a wide range of exercise intensities and environmental conditions, and the overall picture was that fabric type mattered less than most people assume for measurable thermoregulation.
That said, subjective comfort is a different story. Polyester’s low moisture absorbency means sweat stays on your skin longer, which can feel clammy and uncomfortable even if your core temperature is essentially the same as it would be in cotton. Modern polyester activewear uses engineered knit patterns and wicking treatments to move moisture away from the skin and spread it across a larger surface area for faster evaporation. These designs can work well, but they depend on the specific garment construction, not on some inherent thermal advantage of the fiber.
Sleepwear and Sleep Quality
Your skin and body temperature fluctuate throughout the night as part of normal sleep architecture, and what you wear to bed can influence that process. A systematic review examining how sleepwear and bedding fiber types affect sleep found that materials influence sleep quality primarily by affecting skin temperature and thermal comfort.11PubMed Central. How do sleepwear and bedding fibre types affect sleep quality: A systematic review Polyester’s lower breathability and moisture absorption compared to fibers like wool or cotton can contribute to overnight overheating, especially in warm environments. The review did not report a dramatic, universally measured penalty from sleeping in polyester, but the evidence leans toward natural fibers being more conducive to stable thermal comfort during sleep.
The Polyester Underwear Question
One of the more striking findings in this area comes from an animal study that put dogs in polyester, cotton, or no underwear for up to two years. The polyester group showed a significant decrease in sperm count and motile sperm, along with an increase in abnormal sperm forms and degenerative changes on testicular biopsy. The cotton and control groups showed no such changes. After the polyester garments were removed, sperm quality gradually returned to normal in most of the dogs.12PubMed. Effect of different types of textile fabric on spermatogenesis: an experimental study
The researchers suspected that electrostatic potentials generated by the polyester fabric played a role, though they acknowledged the mechanism was not confirmed. This is a single animal study from the 1990s, and it involved dogs wearing tight-fitting polyester underwear continuously, which is not quite how most humans interact with the fabric. No large-scale human trial has replicated these findings. Still, it remains one of the only controlled experiments directly examining how fabric type affects reproductive tissue, and it is cited frequently enough that it is worth knowing about. If male fertility is a concern, it may be reasonable to favor cotton or other natural fibers for underwear while the evidence remains sparse.
The Recycled Polyester Paradox
Recycled polyester, made from post-consumer PET bottles and other waste, is widely marketed as the sustainable choice. From an environmental standpoint, it diverts plastic from landfills. But from a body-exposure standpoint, there is an emerging wrinkle. A study comparing bisphenol A (BPA) levels in clothing made from recycled versus conventional polyester found that recycled fabrics had a noticeably higher mean BPA concentration: about 93.6 nanograms per gram compared to roughly 12.3 nanograms per gram in conventional textiles. The difference did not reach statistical significance in that particular dataset, but the trend raises questions about whether contaminants present in the original plastic accumulate or persist through the recycling process.13PubMed Central. Bisphenols in daily clothes from conventional and recycled material: evaluation of dermal exposure to potentially toxic substances
BPA is another endocrine disruptor, and its presence in recycled clothing could be an unintended consequence of circular-economy efforts. The concentrations detected are still low, and dermal absorption of BPA from textiles is not well quantified. But the finding complicates the simple narrative that recycled polyester is unambiguously better for you, even if it is better for the planet.
Infants and Children as a Special Case
Babies have a much larger skin surface area relative to their body mass than adults, which means chemical exposures per kilogram of body weight are proportionally higher. Research examining heavy metals in infant clothing found that baby garments had the highest hazard indices among the age groups tested, with cadmium in particular exceeding the safety threshold.14PubMed Central. Heavy Metals in Infant Clothing: Assessing Dermal Exposure Risks and Pathways for Sustainable Textile Policies This is not unique to polyester, as heavy metals can appear in any fabric depending on the dyes and treatments used. But given polyester’s association with higher antimony levels and its widespread use in affordable children’s clothing, the combination of vulnerable physiology and synthetic fabric deserves extra caution. Washing new clothes before first wear, choosing certified labels (like OEKO-TEX Standard 100), and favoring untreated natural fibers for items worn directly against infant skin are practical steps.
Microplastics Shed From Your Clothes
Every time you wear, wash, or dry a polyester garment, tiny fibers break off. These microfibers are a form of microplastic, and they end up in household dust, wastewater, and eventually the broader environment. But they also end up on you and in you. A review of human microplastic exposure noted that ingestion, inhalation, and dermal contact are all relevant routes, and that microplastics have been detected in human stool, blood, and various tissues.15PubMed Central. Human Exposure to Microplastics and Its Associated Health Risks Energy balance, gut bacteria, and the reproductive, immune, and nervous systems have all been flagged as potential targets of microplastic toxicity in lab-based studies.
The honest caveat is that most of the toxicology comes from animal models and cell cultures at exposure levels that may not reflect what a typical person encounters. We do not yet have clear evidence that the amount of microplastic shed from your wardrobe is enough to cause measurable harm. What we do know is that the exposure is real and ongoing, that microplastics carry surface-adsorbed pollutants into the body, and that the long-term health consequences of chronic low-level exposure remain an open question. Polyester clothing is, by volume, one of the largest sources of microfiber pollution in indoor environments, so reducing polyester in your daily wardrobe is one of the more direct ways to lower your personal exposure.
Practical Ways to Reduce Exposure
None of this means you need to purge every polyester garment you own. But if you are looking to minimize the chemical and microbial interactions described above, a few evidence-informed strategies help:
- Wash before wearing: A first wash removes a meaningful fraction of residual dyes, antimony on the fiber surface, and loose chemical finishes. This applies especially to children’s clothing and any garment with a strong chemical smell out of the package.
- Favor natural fibers for high-contact items: Underwear, sleepwear, and anything worn tight against skin for extended hours are the highest-exposure garments. Cotton, linen, wool, and silk avoid the antimony and microplastic issues entirely.
- Look for certification labels: Standards like OEKO-TEX and GOTS set limits on harmful substances in textiles, including restricted azo dyes, heavy metals, phthalates, and formaldehyde.
- Wash polyester at lower temperatures: Heat increases both chemical leaching and microfiber shedding. Cooler washes and air drying reduce both.
- Do not assume “recycled” means cleaner: Recycled polyester addresses environmental waste but may carry higher levels of legacy contaminants like BPA. The same precautions apply.
Polyester is not going away, and for many applications its durability, cost, and performance make it a sensible choice. But understanding what it does on your skin, in your sweat, and inside your home gives you a better basis for deciding where in your wardrobe natural fibers might be worth the trade-off.