Why doesn't my deep cut hurt?

Ouch, that hurts: Why paper cuts hurt so much

An innocent sheet of white paper. Looks completely harmless, has hardly any weight and can still hurt like hell. Not just as a farewell letter from exiles. The world in A4 format is often more banal. The copier asks for new lining, a pack of paper is torn open, and it has already happened: the index finger has brushed a sheet too spiritedly, and this impetuous approach is rewarded with a small, painful wound.

Why paper cuts often hurt so much has not yet been systematically investigated scientifically. The dermatologist Hayley Goldbach from the University of California in Los Angeles has several hypotheses. The small cut in the fingertips is so agonizing because there are particularly many sensitive nerve tracts there. The reason: "We discover the world with our fingers. That is why it is important that there are many nerve endings there". Also for our own protection, as this protects our gripping tool from extreme heat, cold and pressure, as the expert explains.

Not deep enough

The nature of the paper is also likely to have a not inconsiderable part of the pain. With the naked eye, the edge of the paper looks smooth and sharp-edged. However, this is a fallacy. A look under the microscope shows the true form of the culprit: the edges are sharp enough to scratch the skin, but not smooth enough for a clean cut. Rather, the paper tears a wound in the skin, "more like a saw than a blade," says Goldbach.

Paradoxically, another problem could be that paper cuts are usually not very deep. However, deep enough to penetrate the first layer of skin. "The concentration of pain receptors is greatest under the surface of the skin," says the dermatologist.

Tear open the wound again

What makes for additional agony: Paper cuts don't go so deep that they really bleed. As a result, the natural protective mechanism such as blood clotting cannot take effect. There is no protective scab surrounding the wound.

Since the small cuts are slow to heal, there is also the risk that they will be torn open again and again. One wrong movement of the injured finger and the wound opens again. It all sounds painfully plausible. (gueb, September 19, 2016)