ABOVE: A photo from a 1923 study showing the effect of blood serum drawn from the arm of a menstruating woman (left) and that of a nonmenstruating control (right) on flowers labeled as cinerea (taxonomy unknown).

One summer afternoon in 1919, Hungarian-born pediatrician Béla Schick handed his maid a bouquet of red roses to put in water. The next morning, he was surprised to see that the roses—which had been ready to burst into bloom the day before—were now dead, their withered petals spilling onto the table. The maid told Schick that the flowers had died because she’d touched them, and that this always seemed to happen when she was on her period. 

For more than a millennium, perhaps stemming all the way back to Roman philosopher Pliny the Elder’s writings in the first century AD, there have been myths about the insidious effects that menstruating women have on their environments, says Open University historian Helen King, naming a few: “If you’re curing meat, it won’t cure properly. If you’re making bread, it won’t rise. If you’re making jam, it won’t set.” She adds that such rumors got “repeated into the 20th century.”

Schick couldn’t believe what he was hearing, but he was a man of science. His eponymous “Schick test,” which he developed in 1913 after moving from Hungary to Vienna, detected preexisting immunity to diphtheria, helping determine who needed a diphtheria vaccine throughout the early 1900s. So when he heard from his maid that her menstrual cycle had somehow killed his roses, King imagines him quipping, “We’re not just going to go by folklore. We’re going to do an experiment!”  

When his maid’s next period started, Schick’s gardener handed her and a control (a nonmenstruating woman) freshly cut anemones (Anemonastrum sp.), white chrysanthemums (Chrysanthemum sp.), and yellow sunflowers (Helianthus sp.). After the women had taken a short walk with the flowers, Schick noted that the menstruating maid’s flowers were already withering, and continued to deteriorate over the next several hours. The control flowers stayed fresh for days. 

Over the next few months, Schick’s experiments with his maid continued. He introduced variables such as the length of time that she and control women handled the flowers and the use of rubber gloves. He also sampled his maid’s armpit sweat, blood, and serum when she was menstruating and tested the effects of these bodily fluids on plants. 

The results were often contradictory—menstruation sometimes had a neutral or beneficial effect on the flowers—but Schick concluded that menstruating women did indeed exude some sort of plant-killing poison. In 1920, he published his results in a Viennese medical journal, calling the substance “menotoxin” (a name he attributed to a certain person by the name of Groër in a footnote)—thus bestowing scientific legitimacy upon centuries of folklore. 

Three years later, two plant physiologists at Johns Hopkins University followed up on Schick’s research, testing the blood, saliva, breast milk, tears, sweat, and even breath of menstruating women. Again, the results were conflicting. The researchers soaked white lupin (Lupinus albus) seeds in different body fluids and watched them sprout, and placed daisy-like flowers labeled as cinereans in dilutions of the fluids and saw them wilt. Nevertheless, their conclusions also supported the idea of the fabled menotoxin.

Investigations of the menstrual poison persisted in scientific publications into the 1970s. In a 1974 letter to The Lancet, University of California, San Francisco, epidemiologist Virginia Ernster said that in the absence of well-controlled menotoxin experiments, photos of wilted flowers “are insufficient data on which to build a case.” Nevertheless, a 1977 letter in The Lancet opined the need for better model systems to study the phenomenon, and a 1979 paper published in a Scandinavian journal speculated that menotoxin might be influencing menstruating women themselves, perhaps by acting on the central nervous system to affect mood changes. 

While menotoxin did eventually fade from the literature, never having been properly demonstrated or fully discredited, the stigma surrounding menstruation as something dirty or shameful remains. A global discomfort with women’s menses has led to increased financial burdens and missed education opportunities for women and girls, and for some, a lack of access to safe sanitation has caused otherwise preventable deaths.

At the very least, many menstruating people have felt pressured to hide their time of the month. “You wouldn’t walk out of a meeting holding a tampon on your way to change it,” says King. “You take the whole handbag and you don’t show anyone.”