Last night, Trump sent all reasonable individuals’ heads spinning when he appeared to suggest during his daily COVID-19 press briefings that injecting disinfectant could help eliminate the virus from people’s bodies.

“I see the disinfectant where it knocks [the virus] out [from a surface] in a minute, one minute, and is there a way we can do something like that [by] injection inside or almost a cleaning, because you see it gets on the lungs and it does a tremendous number,” he said as Dr. Deborah Birx, the coordinator of the White House COVID-19 task force, looked visibly incredulous in the background.

Trump also indicated during the briefing that ultraviolet light could help rid patients’ bodies of the virus: “supposing we hit the body with a tremendous, whether it’s ultraviolet or just very powerful light and I think you said that hasn’t been checked but you’re going to test it. And then I said supposing you brought the light inside the body, which you can do either through the skin or in some other way.”

At first glance, it would appear that Trump’s comments are so outlandish and ridiculous as to not even be worth debunking. But the truth is that both bleach ingestion and UV light exposure have circulated as potential cures during the pandemic, even though the World Health Organization (WHO) formally debunked the latter in March by asserting that UV light can cause skin irritation.

The UV light claim is ostensibly based on a Homeland Security study suggesting that UV light can kill the virus on surfaces and in air. “On a surface it’ll kill it quickly,” says Kenneth R. Weinberg, an emergency room physician in New York City. “[But] the thought that somehow UV light that’s shined on a person could get in there or bringing the light inside — I have no idea what hes talking about. How would that be done? A colonoscopy? A bronchoscopy? How do you get light into somebody’s body?”

Bleach in particular has been touted as a medical cure for everything from seizures to autism for years in some conspiracy theorist circles, and have gained steam during the COVID-19 pandemic. As NBC News reports, proponents of Mineral Miracle Solution (MMS), a diluted form of bleach that has been roundly debunked by medical experts, cheered on Trump’s comments on Thursday night, with one QAnon supporter writing that the product served as “a good lung cleaner.”

Dr. Peter Chai is an assistant professor in the Emergency Medicine Division of Medical Toxicology at Brigham and Women’s Hospital in Boston. He says that most of the time, when he sees people injecting bleach, it’s usually IV drug users, due to an urban legend that it can clean your blood of impurities after you use heroin and methamphetamine. He says that when people have done this, the side effects are absolutely horrifying.

“Bleach is a caustic agent. It’s the opposite of an acid, because it’s more alkaline. It breaks stuff apart, which is why it works to clean surfaces,” he says. “So when you think about injecting into your veins, it’ll break things apart in your blood.” That usually results in hemolysis, or the red blood cells that carry oxygen in your body breaking apart, so oxygen can’t be carried into your vital organs. This can result in blood clots, liver injury, or most frequently, kidney injury or failure, which could be bad enough that it could be permanent and require dialysis.

It’s more common for patients to ingest rather than inject bleach, usually small children who’ve accidentally done so (indeed, Chai says there’s been an increase of calls to poison control centers during the pandemic, mostly from panicked parents who’ve left bottles of cleaning products lying around) or adults who do so purposefully in an attempt to take their own lives. Depending on the dose, this can be fatal. “A lot of the common cause of death is GI injury or burns in the stomach or esophagus,” he says. “[Ingesting bleach] can tear those places open and you can die from that.”

At the end of the day, most reasonable people will not adhere to Trump’s medical advice. But the fact that a man with one of the biggest platforms in the world used it to advocate for dangerous and unfounded medical advice during a time of high national anxiety will likely have serious consequences, Chai worries.

“As a physician and as a toxicologist, we worry that people will do some of these things,” he says, adding that he’s already seen patients reporting complications from hydroxychloroquine, another “cure” that Trump has touted. “[From a public health perspective, our health care system is already stretched so thin that we’d ideally like not to manage a second series of patients with complications who decide they want to inject bleach or ingest a disinfectant.”