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Michael: There you are, reading a book in bed after a long day. You finish the chapter and go to close the book and... Ow! Paper cut! Paper cuts are usually small and shallow, but they do tend to hurt a lot, for a few reasons.

There’s the fact that most paper cuts happen on your hands, since you don’t usually try to move pieces of paper with, like, your legs. You’re going to pay more attention to an injury when it’s on a body part that you use all the time, your brain thinks about your hands at least 10 times more than your arms or your legs. And of course, thinking about your cut means you’re focusing on the pain.

Plus, cuts on your fingertips are just more painful in general. Since you mainly use your fingers and your hands to feel the world around you, they’re full of nociceptors, pain receptors that respond to things like pressure and temperature. Paper cuts directly damage the nociceptors in your outermost layer of skin, the epidermis, and those nerve bundles send pain signals to your brain.

Considering your hands have more nociceptors per square inch than almost any other part of your body, it makes sense that a paper cut on your hand would be much more painful than a paper cut on, say, your arm. Plus, of the different kinds of everyday objects that could cut you, paper is one of the most jagged.

A knife will generally leave a clean, residue-free cut, but dull, flexible paper will tear your skin cells apart like a saw. Paper can also leave fragments and chemicals behind that irritate your vulnerable inner skin layer, or dermis. Even with all that skin damage, many paper cuts aren’t deep enough to hit blood vessels, so there’s very little bleeding or clotting, which actually makes things worse.

Without a scab to protect the exposed tissue, every little thing you do can stimulate pain receptors. And superficial hand wounds take a long time to heal. When you use your hands to do things, wash dishes, play guitar, carry groceries, your paper cut keeps tearing and getting dirty, increasing the healing time.

So there are lots of different factors that combine to make paper cuts more painful than you’d otherwise expect from such a shallow cut. Hands and the edges of paper are just a bad combination.

Thanks to Patreon patrons UrbanAbydos and Elvina Lui for asking, and thanks to all our patrons who keep these answers coming. If you’d like to submit a question to be answered, just go to Patreon.com/SciShow, and don’t forget to go to YouTube.com/SciShow and subscribe.