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Polyester certainly isn't on a pedestal as a quality material, but most people don't think twice about wearing it. Buy the cozy sweater, the jammies, or the hat. No big deal, right?
Polyester is everywhere, from underwear (most bras) and t-shirts to blankets, pajamas, socks, active & swimwear, and bedding. It's inexpensive, durable, and can be fluffy soft.
But what if there's more to this ordinary fabric than meets the eye.
Researchers investigating the effects of different textiles on their very favorite subject, dogs, uncovered some rather surprising findings.
Polyester and Males
In a 1993 experimental study, researchers examined the effects of polyester underwear on sperm production in male dogs. Twenty-four dogs were divided into groups wearing either 100% polyester or cotton underwear, with additional dogs serving as controls.
The dogs wore the underwear continuously for 24 months.
Putting aside the adorable imagery, the results were striking. Dogs wearing polyester experienced significant reductions in sperm count and sperm motility, along with an increase in abnormal sperm. Researchers also observed changes in testicular tissue.
The good news is that after the polyester garments were removed, sperm quality gradually improved in most of the affected dogs.
Polyester and Females
In a separate 2008 experimental study, researchers followed 35 female dogs wearing garments made from polyester, polyester-cotton blends, cotton, or wool over a 12-month period.
The findings were very interesting. All eight dogs wearing polyester-containing fabrics experienced reduced progesterone levels and failed to conceive. After the garments were removed, hormone levels returned to normal, and the dogs were subsequently able to conceive.
The researchers explored whether electrostatic charges generated by synthetic fabrics might contribute to these effects.
Polyester and Pregnancy
A 2007 study published in Clinical and Experimental Obstetrics and Gynecology followed 35 pregnant dogs wearing garments made from polyester, cotton, wool, or polyester-cotton blends, monitoring their reproductive hormone levels throughout pregnancy.
Of all 35 dogs participating in the study, only those wearing 100% polyester experienced miscarriages. Two of the seven dogs in this group experienced significant declines in progesterone during the first month of pregnancy and subsequently miscarried. The remaining five delivered healthy puppies, as did all 28 dogs in the other groups.
Interestingly, the two dogs that miscarried later became pregnant again without wearing polyester and delivered healthy puppies.
The researchers suggested that electrostatic effects might have played a role, although they could not establish the cause of the miscarriages.
Polyester and Hair Growth
Another 1993 study investigated whether different fabrics could influence hair growth.
Researchers examined 40 dogs and covered shaved areas of their skin with polyester, cotton, or wool textiles.
After two months, the polyester-covered areas demonstrated significantly reduced hair growth. Researchers also observed lower hair density, thinning of the epidermis, and structural changes involving hair follicles.
Cotton and wool did not produce these effects.
Yes, There Are Human Studies, Too!
In a 1992 study published in Contraception, 14 healthy men wore specialized polyester scrotal slings for 12 months. All 14 developed azoospermia, meaning no detectable sperm in their semen. Sperm production gradually returned after the polyester garments were removed. The researchers described this as a potentially reversible form of male contraception.
Another 1992 study involving 21 men investigated the electrostatic charges generated by different fabrics against the scrotal skin. Pure polyester produced substantially higher electrostatic potentials than cotton or polyester-cotton blends.
A 2009 study published in Occupational and Environmental Medicine examined 1,752 female textile workers in Shanghai. Researchers found increased odds of miscarriage among women occupationally exposed to synthetic fibers, including polyester. Women exposed to a mixture of synthetic and natural fibers also showed increased miscarriage odds.
A more recent 2023 study published in Science of the Total Environment examined 120 clothing samples marketed to pregnant women, newborns, and toddlers. Researchers detected bisphenols, including BPA, in the clothing samples, with the highest BPA concentrations found in polyester garments.