Paper Cuts

Medical Topic of the Day:  Paper cuts are annoying but how do they happen and what is the mechanics involved.


Off the Top of My Head:  I know you can get a paper cut from other things that aren't paper. I don't understand the exact mechanics involved though

My Research Today:  Your integumentary system, your skin, protects you from the ravages of the outside world.  How can something like paper cut your skin and make you bleed?

Well your skin is an assortment of collagen fibers and it is specifically arranged to withstand pinpoint forces.  Unfortunately this makes your skin weak against shearing forces, that is thin things sliding against it.

Something about shearing force.

The average sheet of paper is just 0.1mm thick.  A human hair is approximately 100 microns thick.  A 1000 microns equal 1mm, so a human hair is about as thick as a piece of paper.  If your skin slides along something that thin for even a short amount of time it will just break the epidermis, which is the outermost layer of your skin.

This injury exposes many nociceptors which are pain receptors.  This is why paper cuts hurt.  The pain receptors are exposed to the open air.  Also the fibers in the paper may contribute to the irritation as well.

So now you know why paper cuts suck so bad.