The human body is fascinating, complex, and, if you look a little too closely, deeply unsettling. While we tend to think of our bodies as well-oiled systems that quietly keep us alive, the reality is far stranger and sometimes downright disturbing. From bizarre biological quirks to unsettling processes happening beneath your skin right now, the human body has no shortage of facts that can make you squirm.

Inspired by a Reddit thread asking , “What’s a creepy fact about the human body you wish you never found out?”, this list gathers some deeply uncomfortable truths that might make you see yourself a little differently. Read on if you’re curious, but consider this your warning, once you learn these facts, you can’t un-know them.