A claim circulating on X suggests that polyester clothing acts as a form of birth control, referencing a study on dogs as evidence that wearing polyester could impair human fertility.
The post states that, in the study, 75% of female dogs wearing polyester suffered from reduced progesterone levels, inhibiting their ability to get pregnant, and extends the claim further to assert that polyester is “loaded with endocrine disruptors” that damage fertility.
Published on 20 May 2026, the post has since garnered over 20,000 views. With Singapore’s fertility rate already a topic of public conversation, with a historic low total fertility rate of 0.87 in 2025, claims linking everyday items like clothing to fertility are likely to catch people’s attention. We decided to take a closer look at what the science actually says.
What is polyester?
Polyester is a synthetic fabric made from petroleum-based plastic polymers. First developed in the 1940s, it has since become the world’s most widely produced textile fibre, valued for its durability, wrinkle resistance, and low cost. Today, polyester accounts for approximately half of all global fibre production and is found in everything from clothing and bedding to upholstery and industrial materials.
What was the study about?
The post references ‘a study’ without specifying which one, accompanied by what appears to be a table from a 2008 study published in the Journal of Obstetrics and Gynaecology by Ahmed Shafik, a surgeon from Cairo University’s Faculty of Medicine in Egypt. In the study, 35 female dogs were divided into five groups. One control group wore nothing while each of the four test groups were dressed in underpants made from a different fabric: 100% polyester, a 50/50 polyester-cotton blend, 100% cotton, or 100% wool, worn continuously over 12 months. The researcher then tracked whether the dogs could conceive and measured their hormone levels throughout.
The post claims that 75% of dogs wearing polyester failed to conceive. However, a closer reading of the study does not appear to support that statement. Of the 35 dogs, 14 dogs wore polyester-containing fabric (either pure polyester or a polyester-cotton blend), and of those, eight failed to conceive, which amounts to approximately 57% and not 75% as the post claims.
The post also states that polyester ‘tanked’ progesterone – a hormone essential for preparing the body for pregnancy — implying a lasting effect on fertility. However, five months after the garments were removed, progesterone levels in all eight dogs normalised and they went on to conceive, suggesting the effect was temporary rather than permanent.
Shafik’s proposed mechanism was also notably different from what the claim implies. Rather than attributing the effect to chemical endocrine disruptors leaching from the fabric, Shafik theorised that the static electrical charge generated by polyester against skin created an electrostatic field that may have interfered with ovarian function.
It is also worth noting that Shafik’s body of work on polyester and fertility was largely conducted by one researcher and has never been widely replicated. His human studies involved very small sample sizes, one experiment featured just 21 male participants, making it difficult to draw broad conclusions about polyester’s effects on human fertility from his research alone.
What does available evidence say?
The claim also asserts that polyester is “loaded with endocrine disruptors”, chemicals that interfere with the body’s hormonal system, potentially affecting reproduction.
Some polyester products do contain chemicals of concern. For example, antimony trioxide, typically used as a catalyst in the production of polyester, is classified as a suspected carcinogen and can remain as a residue in finished garments. Research has shown it can migrate into sweat under lab conditions, though the concentrations measured are typically low. The study also found that washing garments before use can minimise exposure.
It is also worth noting that these chemicals are not inherent to polyester itself, they are byproducts of manufacturing, meaning the risk varies depending on where and how a garment was made.
The claim’s broader implications have also been examined by health experts. In a January 2026 interview with NPR, the American public radio broadcaster, on whether polyester poses health risks, Ryan Marino, a medical toxicologist at Case Western Reserve University in the U.S., stated that it has not been proven that polyester causes infertility in humans. He added that unless someone is living near a landfill or regularly handling large quantities of polyester, they are unlikely to encounter a dose of chemicals that would cause significant health concerns.
Conclusion
The post appears to misrepresent the findings of the study it references. The 75% figure does not seem to correspond to the study’s data, the effects observed were temporary and reversible, and the research was conducted on animals, not humans.
While some polyester products do contain chemicals of concern, current evidence does not support the assertion that wearing polyester impairs fertility. Therefore, we rate the claim that polyester inhibits fertility as partly false.
When encountering claims like these, it is worth remembering that a single animal study cannot be generalised to an entire human population. It is good practice not to take claims at face value simply because a study is cited.
