This is the edge of a paper under the electron microscope: the reason why cuts with sheets and folios hurt so much

Yesterday I cut a finger with a bread knife. Unintentionally, I must add. And no, it was not an analysis of knives that got out of hand: it was an accident. Although I must say that, although the 'first impressions' were not good, the knife cut well: I do not know if it would give it ten stars, but I do know that they gave me four points.

So when this morning I have seen people talking about why a cut with a sheet of paper hurt so much, I have seen it as a sign. I would lie to you if I told you that the idea of ​​making a cut with a sheet of paper to compare with knowledge of the cause has not crossed my mind, but in the end sanity has prevailed and I have started diving online. Why does a paper cut hurt so much?

A little studied question

All you have to do is search on the net for you to verify that a lot has been written on the subject, but very little research has been done. Fundamentally because there is no ethics committee that approves of torturing research subjects only to satisfy a curiosity as cloudy as it is useless (however recurrent it may be). When it comes to contemporary science, sadism only has room in sexology laboratories.

And of course, in the absence of good research, what we have left are the hypotheses. And there are many, but those related to anatomy are the most popular. Does a cut on the fingertips hurt the same as an equal (identical, clonic) cut on the arm or calf? I know that pain is one of the most personal, non-transferable and subjective things that exist, but let's grant the mental experiment.

And regardless of the result, anatomical logic tells us no. The areas where we usually have paper are not only strongly enervated, but are full of nociceptors, the receptors for negative stimuli. That is, those responsible for translating tissue damage or irritation into pain.

It makes sense, although as a victim of a self-inflicted knife-in-hand attack, I just didn't see this as the essential difference. I can admit the idea that since paper cuts don't usually bleed, the healing process (through coagulation) is more cumbersome and complex. But that is, in any case, an explanation for the reason that it takes longer to heal, not that it hurts more.


Hmmm ... The explanation that convinces me the most is that, although it does not seem so with its straight, white and sharp lines, the paper is very rough at a microscopic level. Unlike the sharp metal knife, the paper acts on the wound as if it were a sandpaper and that, of course, is much more abrasive for cells and nerve endings.

The image up there is speaking for itself: the edge of a paper under the electron microscope. With that image in mind, paper cutting suddenly seems like a really terrible thing. In addition, it appears that the paper also leaves small fibers and chemical residues that favor much greater wound irritation. Don't call it 'paper', call it 'being a damn party for nociceptors'. A party that, apparently, it is very painful.

Image | PSU

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