The United States’ Food and Drug Administration (FDA) issued a statement on Saturday warning citizens to stop taking a horse deworming drug as defence against COVID-19, following reports of people being admitted to hospital after taking it. The FDA even posted the message to social media in an effort to get the word out: “You are not a horse. You are not a cow. Seriously, y’all. Stop it.” The medication, known as ivermectin, is often used to treat or prevent parasites in animals, according to the organization, which has “received multiple reports of patients who have required medical support and been hospitalized after self-medicating with ivermectin intended for horses.” It is not in any way an antiviral drug, though in certain cases humans can use it; it’s approved by the FDA to treat people with intestinal strongyloidiasis and onchocerciasis, two conditions caused by parasitic worms. In some cases of head lice and rosacea, topical versions of ivermectin are approved as well — but that’s the extent of it. It has no ability to protect humans from COVID-19 or any other sort of viral invader.