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Why do paper cuts hurt so much?

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📓 The short answer

Paper cuts hurt so much because they cause jagged wounds, hit densely packed nerve endings in your fingertips, and are shallow enough to stay exposed without quick healing.

📚 The long answer

While much of our daily lives has gone digital, we're still at risk of getting the occasional paper cut. But they make such tiny cuts – why in the world do they hurt so much?

Science hasn’t definitively answered this question, possibly because few people volunteer for paper cut research (ouch). But we do have some solid theories to explain why paper cuts hurt so much.

Reason #1: Paper doesn't make a clean cut on skin.

Paper feels smooth to the touch, but under magnification, its edge is rough and jagged. See this 100x magnified picture of the edge of a piece of paper below.

When the paper cuts your skin, it cuts more like a saw than a knife, ripping and shredding your skin. This causes more cellular damage than a clean cut, which adds to the pain you feel.

Reason #2: Nerve endings are concentrated in our fingertips.

Since humans tend to touch things with our hands, our bodies have evolved to concentrate a high density of endings in the fingertips. This makes sensations like touch, pain, heat, and pressure much more acute in a fingertip than in other areas, such as a thigh.

You can actually prove this with a simple at-home test. Take a paper clip and unfold it so that both ends are pointing in the same direction. If you touch both ends on your fingertips, you can tell that there are two pokes. Now try the same on your thigh. You'll probably need to space apart the paper clip ends pretty wide before you're able to sense that there are two pokes.

This phenomenon is known as "two point discrimination," which refers to the ability to distinguish between two points of touch. The density of nerve endings in different areas of the body determines how far apart these points need to be in order to be perceived as separate stimuli.

The dense nerve endings in your fingertips make paper cuts especially painful. Word of advice: Also try to avoid paper cuts on your lips, tongue, and genitals, body parts which are similarly sensitive. 😳

Reason #3: Paper cuts are deep enough to hit nerves but shallow enough to not cause scabbing.

Part of the reason why paper cuts feel so painful is because they hit a sort of "goldilocks" zone of your skin. They cut deep enough so that they hit your nerves, but shallow enough that they don't hit your blood vessels.

The paper cuts through your epidermis but not far down enough to your fat layer. This makes the cut perfect for exposing and triggering the nerve endings to send pain signals to your brain. However, it doesn't reach far enough to cause enough bleeding to help heal the wound quickly and protect the nerves with clotted blood. Because paper cuts remain exposed, they take longer to heal and cause more pain than deeper cuts.

Reason #4: There's a high likelihood of reopening a paper cut because of our frequent use of fingers.

Unless you take the time to clean and bandage your office work flesh wound, you're likely to reopen the cut, restarting the pain cycle.

🧠 Bonus brain points

What kind of paper is most likely to cause paper cuts?

A 2024 study out of Denmark decided to answer the pressing question: What kind of paper is most likely to cause paper cuts? Fortunately no research participants were needed; the study simulated paper cuts on ballistics gelatin trying to induce a cut with different types of paper.

Researchers found that paper of a certain thickness is most likely to cause cuts. Paper that's too thin, like tissue paper, buckles and bends under the pressure and doesn't make an incision. Too thick, like photo paper, and it simply presses into skin. But paper that's around 65µm (micrometers) thick, like newspaper, magazine, or dot-matrix print paper, is the most likely to cut through skin.

I'll keep my digital subscriptions, thank you very much.

--- Thanks for reading this week's newsletter! If you have any thoughts, questions, or favorite GIFs, my inbox is always open. Just hit reply to send me a note! :) ​ All my best, Caitlin ​Click here to read five facts about Caitlin​

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​Sources for this week's newsletter​

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P.S. If you dare, check out this horrifying depiction of finger tips I came across in my research. I will never unsee this. ✋🫣

📖 Book of the week

​This Idea Must Die: Scientific Theories That Are Blocking Progress edited by John Brockman​

I have to confess, part of the reason I spotted this book at the library was because of its shiny cover. But I'm glad I checked it out because it's packed to the brim with interesting essays about science. In 2014, 175 scientists, researchers, and philosophers were asked about an idea that should be put to rest. Arguments included getting rid of "left brain vs. right brain", limitless economic growth, and even the concept of true and false. Admittedly, I did skim or even skip some essays I wasn't interested in reading, but there's enough thought-provoking pieces that kept me fascinated the whole way through.

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​Check out the full list of books I've recommended here.

👀 Catch up on other curious questions

• ​Why are most people right-handed?​​
• ​How does popcorn pop?​​
• ​Why do harmonies sound good?​​

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