A piece of paper is a harmless object, until its edge cuts into the tip of your finger. Journalist Jason Goldman of the British broadcasting company BBC tried to find out why these cuts are so painful.
Not much research has been made into these so-called paper cuts, but the reason why they're so painful is probably a combination of two factors. First of all, the tips of our fingers are very sensitive, because this is a place where many nerve endings come together. "If you would have a paper cut in your face or your genitals, this would also be very painful", dermatologist Hayley Goldbach tells the BBC. "Our finger tips are the body parts with which we explore the world and execute delicate little tasks. So it's logical that we have many nerve endings there, it's a kind of safety mechanism". When you encounter something sharp or warm, chances are that the first point of contact will be your hands. The fact that your fingertips hurt more, is quite logical, evolutionarily speaking.
A blunt saw
Secondly, there's the paper itself. Paper is porous matter and the edges are, seen from very close-by, not as straight as they might seem. The edge of a sheet of paper is more like that of a blunt saw than that of a sharp knife, resulting in a chaos of tears and folds in the sheet. Moreover, paper cuts fairly deeply: "Deep enough to cut through the upper skin layer, because else it would not hurt", Goldbach says. "The upper skin layer has no nerve endings". When you have a paper cut in your finger, it is best to take good care of it. Chances are that the piece of paper is densely populated by bacteria which love to settle in your wound. These won't hurt you at the moment when you cut yourself, but they can cause infections afterwards.