You probably haven’t heard of Sandra Lee, a board certified dermatologist in California. But you might know her by her alias, Dr. Pimple Popper.

She posts videos doing exactly what she advertises: clears out large, pus-filled blemishes (and treats other dermatological conditions, too). It’s objectively disgusting. And yet, Lee has about 2.5 million subscribers on Instagram and Youtube, with over 1 billion views on the latter. You would think that most of us have more pleasant ways to spend our time on the internet—and yet it’s clearly hard for people look away.

There’s actually a psychological explanation for loving these videos—or at least voluntarily watching more of them even when they make us uncomfortable. “People are often drawn to things that bother them,” says Alexander Skolnick, a psychologist at Saint Joseph’s University who studies what is possibly the most under-appreciated emotion: disgust.

Disgust is a feeling we’ve carried with us since our ancient, reptilian brains had to figure out how to keep us alive. We tend to feel it when there’s something harmful around: We know snakes and some insects mean danger. Vomit means something made someone else sick. Poop carries diseases. When we see any of these, we naturally want to avoid them.

Just about opposite of disgust on the human emotional color wheel, there’s curiosity, which draws us into explore. Whereas disgust repulses us, As BBC reports, our brains have made us sponges for learning. We’re wired to collect information when it’s available to us.