After more than 50 days of nightly protests against racism and police violence, demonstrators in Portland are intimately familiar with the immediate effects of tear gas: blurry eyes, burning skin, choking, coughing, crying, retching.

But some protesters believe the gas is doing more than causing red eyes and seething skin. OPB interviewed 26 protesters, ranging in age from 17 to 43, who said they believe regular exposure to tear gas has caused irregularities within their menstrual cycle.

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The experiences range. Some protesters reported getting their period multiple times in a single month. Others reported debilitating cramps — at least one that ended in a hospital visit — and blood clots the size of half a fist. Trans protesters who had stopped menstruating since taking testosterone said they have seen their cycles restart.

There are two common threads between the experiences of the 26 protesters: All said what they were experiencing was abnormal for their bodies. And all believed the tear gas, which law enforcement has been using against demonstrators for two months, was at fault.

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There has been little scientific research into whether tear gas can affect a person’s hormones — and experts warn against extrapolating a solid medical conclusion from anecdotal evidence. But while the science remains thin, the troubling stories have mounted as the release of the chemical has become a near-nightly occurrence.

Lindsey Smith, a 26-year-old preschool teacher who has been live-tweeting the protests since mid-June, said she’s noticed a pattern: If she inhales a significant amount of gas in the night, she’ll have her period the next morning. She said this has happened at least three times in two months — even though the hormonal birth control she’s on makes it so she’s only supposed to menstruate four times a year.

On July 12, after another night that saw federal officers blanket the crowd with tear gas, Smith tweeted to ask if anyone else was menstruating after being exposed to the gas. She received nearly 30 responses from protesters with their accounts of irregular periods: cramping within hours of exposure, periods that stretched for nearly a month, or arrived weeks early.

She was also met with some trolls.

“When I posted that, there were a lot of alt-right people screenshot-ing it and reposting it — and a lot of them are saying, ‘Good, I hope after this you’re sterile,’” she said. “That was the first time that the thought occurred to me: I don’t know what this is going to do. And I don’t think anyone really knows long-term.”

Evidence, but no firm proof

Within the small body of research that does exist on tear gas, the question of what effect it could have on a person’s reproductive health, if any, has been left unanswered.

Sven Eric Jordt, an associate professor at the Duke University School of Medicine who has extensively studied tear gas agents, said it’s possible the gas impacts hormones. He pointed to a 2010 study that showed burning the agent in CS gas, a common type of tear gas, could generate chemicals potentially toxic enough to affect hormonal homeostasis. Researchers in Chile raised concerns tear gas might cause miscarriages in 2011, leading the government to temporarily ban its use. In Bahrain, Physicians for Human Rights documented accounts of pregnancy loss among civilians gassed during anti-government protests.

But no one can say with certainty if there’s a link.

“There’s really no data on this. It’s entirely possible that some of these chemicals that if you inhale them at high levels can have effects,” Jordt said. “But it’s really hard to say.”

Intense stress could be another culprit. Rising levels of cortisol, the body’s primary stress hormone, are known to upend normal menstrual cycles, And the policing tactics common among local and federal officers — including tear gas, impact munitions, and flash bangs — could all be fairly described as cortisol-inducing. Not to mention the new unusual rituals that could potentially alter someone’s usual menstrual cycle: bedtimes pushed to the early morning, a diet of snacks and energy drinks, nightly sprints away from gas and police.

But some protesters in Portland are convinced that stress alone can’t explain their experiences.

While many nights are traumatic, protesters are not breathing lungfuls of the chemical every single evening. And some report it’s only in the aftermath of these hazy nights, during which they’ve inhaled for minutes without a mask, that they notice the irregularities.

Alissa Azar, 29, has been protesting downtown at least five nights a week since the demonstrations began. She said she’s been caught in the thick of a cloud of gas six times. On two of these occasions, her period started immediately after. The other four times, it started within a few days.

“Obviously we’re experiencing a significant amount of stress right now physically, mentally, emotionally. It would be naive to believe that doesn’t have an effect. However, I definitely think there’s a correlation between menstruation and tear gas,” she said. “The timing has been too spot-on.”

She said the periods are different than what she expects. Each one lasts for four or five days. The cramps are more like the contractions she had when she gave birth, inducing nausea and severe back pain. A dozen other protesters interviewed had similar accounts of cramps that felt like sharp rocks being cradled in their stomachs.

“We’re not paranoid. This isn’t a coincidence. Something’s going on,” Azar said. “Within 15 minutes of a gas attack, myself and others will have to take a break from how bad the cramps are.”

Dramatic physical and psychological impacts

For some, the experience goes beyond physical pain. Five transgender individuals taking testosterone, which typically stops menstruation after a matter of months, told OPB they’d seen their cramps and bleeding return after attending demonstrations.

These protesters say these unexpected periods were accompanied by a sense of gender dysphoria, the clinical term for the discomfort and distress people feel when their bodies don’t align with their gender.

“It’s definitely a back and forth feeling. I’m still pretty early in my transition, and I’ve waited a really long time to be able to do this,” said Lester Lou Wrecksie, a nonbinary transmasculine person who has been taking testosterone since September.

Wrecksie, 43, said on most nights they stay in the back of protests, largely out of the way of gas. But on June 21, they got knocked down and ended up getting caught in the chemical for longer than usual. Two days later, Wrecksie said their cycle returned for the first time in half a year.

“It’s unsettling to be like, I can go out into the air with chemicals and have it basically undo part of what I’m trying to do for myself,” they said.

A few protesters said they were concerned enough with the period irregularities that they scheduled a call with the local Planned Parenthood. Paula Bednarek, the medical director for Planned Parenthood Columbia Willamette, said clinicians had not noticed an uptick in patients reporting unusual menstruation since the protests began.

But enough reports linking period irregularities and tear gas have cropped up nationwide in the last few months that another branch of Planned Parenthood has taken note. An epidemiologist with Planned Parenthood North Central States, which supports reproductive health in Iowa, Minnesota, Nebraska, North Dakota, and South Dakota, crafted a research proposal after putting out a call for reports from protesters who’d spontaneously menstruated after being tear-gassed. A handful of online outlets have also done write-ups this summer questioning a possible connection between the chemical and periods.

Dr. Rohini Haar, a medical expert for Physician for Human Rights, said while these experiences should be acknowledged, she believed there is danger in overreporting a potential link without the hard scientific evidence to back it up.

Haar, an expert in crowd control weapons who has studied the health consequences of tear gas up close among Palestinian refugees, said she’d only started hearing these anecdotal reports of tear gas affecting menstruation a few weeks ago. She worried these new accounts could genderize protests and lead to a narrative that protesting is only safe for people without ovaries.

“This may be an issue, but it’s certainly not enough of an issue to intimidate people away from protesting — especially women,” she said. “It’s not the situation where you should tell your teenager, ‘This definitely injures your reproductive tract, you are not allowed to go.’ There is no evidence to say that.”

Dr. Jordt said he thought it would be worth trying to find out. He suggested a local or state health department in Oregon should initiate a study, taking health data from protesters and residents and following up with them over the long term.

Jordt estimates there are currently five or six of these sorts of studies that look at long-term effects of tear gas on people who have been exposed repeatedly, most coming from the Middle East during the Arab Spring. But he said governments in these countries often hampered the efforts of the doctors leading these studies, making it difficult to follow up with civilians over long periods of time.

One of the most comprehensive studies within the United States was conducted on recruits for the U.S. Army in 2014. Researchers found recruits exposed to CS gas as part of a training exercise were at a higher risk for developing respiratory illnesses, including influenza, pneumonia and bronchitis.

They were exposed to the gas just once.

Jordt pointed to two reasons why learning the long-term health effects of repeated exposure to tear gas has yet to become a top concern of health experts in the United States: The first is that it’s rarely used at the levels the country has seen this summer. While it’s been used en masse on protesters before — in Ferguson, Missouri, in 2014, during the Occupy Wall Street movement in 2011, during the Vietnam War protests in the ’60s and ’70s — he said the chemical hasn’t been pervasive enough to become a top priority among health experts.

Nor is it top of the list for law enforcement agencies. Jordt said there’s a strong belief among law enforcement that teargas is their safest option for controlling crowds. He suspects they will not be the ones leading the charge for a deeper study.

The lack of concrete studies has left some protesters feeling like guinea pigs, scouring Google for answers on what’s happening to their bodies with no satisfying results.

“We don’t know the long term effects of this,” said Elisa Blackman, 24, who said she got her period five times between June 2 and July 5. She tried to search for an explanation, but the hits she got on the internet focused on effects you could expect in the minutes after being gassed, not weeks or years.

“It’s like they’re testing it on us.”