There was a time when wearing polyester pants might actually increase reproductive success.
There was a time when wearing polyester pants might actually increase reproductive success. Waring Abbott/Getty Images

Static electricity can be a real pain. It can make your hair frizz out, it can zap you when you turn on the lights, and, according to one scientist, it can even affect fertility. But you don’t have to worry about the charge created when you shuffle across carpet. A small body of research, all conducted by one doctor in Egypt, says you might want to worry about the polyester pants lurking in the back of your drawers.

The late Ahmed Shafik was an incredibly prolific researcher who published more than 500 scientific papers, primarily on the subjects of urology and reproduction. He innovated bladder transplantation techniques and ideas for urinary diversion. He described the muscle reflexes involved in sex, and spent a year in prison for working on an artificial bladder. And a handful of his papers, most of them published in the early 1990s, suggest Shafik was also deeply suspicious of polyester. One paper describes an experiment on dogs that investigated the effects of polyester on hair growth. Another had study participants put on and take off wool and polyester hats to measure the static electricity generated.

One study’s frank title belies the quirkiness of the experiment it describes. “Effect of Different Types of Textiles on Sexual Activity: Experimental Study” doesn’t tell you that rats wearing pants were involved.

Rats. In pants.

White? After Labor Day?
White? After Labor Day? Jean-Etienne Minh-Duy Poirrier/CC BY-SA 2.0

Shafik dressed 75 male lab rats in tiny little underpants, some of cotton, some of wool, others of 100 percent polyester, and some of a polyester/cotton blend. The rats wore these pants for six to 12 months, and Shafik tracked their sexual activity. He also measured the electrostatic potential on each rat’s penis and scrotum with, it’s probably safe to assume, very small electrostatic probes. Shafik found that the pure polyester and polyester blend pants generated a static charge—and he hypothesized that this may help explain why these rats were not as successful when it came to their sexual advances. He published the results in the journal European Urology in 1993.

He performed similar experiments on dogs. One study had female dogs wear the same types of pants as the rats (presumably in a larger size) and tracked whether they conceived. In another, “the effect of different types of textiles on pregnancy was studied in 35 pregnant bitches.” In still another, male dogs wore cotton or polyester pants for two years, and Shafik found the dogs in polyester pants had lower sperm counts. “The cause of this effect is unknown,” he wrote in the journal Urology Research, “but it may be assumed that the electrostatic potentials generated by the polyester fabric play a role in it.”

As with many clinical trials, eventually the experiments moved from animals to humans. After tracking the sexual activity of 50 men wearing underwear made of the same four fabrics he had tested on rats and dogs (a control group went commando), Shafik determined the polyester pants had an “injurious effect” on human sexual activity. He also tested a potential male contraceptive on humans—a polyester sling. The men in the study wore the sling for a year, and after an average of about 140 days, they stopped producing viable sperm, he reported. Once they took off the slings, things eventually returned to normal.

Polyester comes in many forms, none of them suitable for everyday underwear, just to be on the safe side.
Polyester comes in many forms, none of them suitable for everyday underwear, just to be on the safe side. Brett_Hondow/Public Domain

Today’s polyester pants tend to be more of the athletic variety, compared with the distinctive suits of the 1960s and ’70s. But if you’re eyeing your workout clothes with suspicion, you probably don’t need to worry. Shafik’s human experiments didn’t have many participants; 14 subjects are certainly not enough to definitively declare polyester slings effective birth control. Also, Shafik’s volunteers all wore their polyester undergarments every single day for at least six months. Chances most wardrobes wouldn’t present this problem.

Shafik passed away in 2007, without having left us any idea of what sparked his interest in the safety of polyester underwear. His work on rats and the sling contraceptive earned him a posthumous Ig Nobel Prize in 2016—a tongue-in-cheek award dedicated to the corners of science that sound absurd but still provoke thought. His work, unusual as it seems, certainly has a place in the sexological tradition, from Freud to Gräfenberg to Kinsey.