When I was just a young boy, I slammed my thumb in a car door. That fingernail proceeded to fall off about a week later, revealing a brain-like section of skin that both intrigued my boyish self and absolutely terrified every normal adult who had the misfortune of seeing it.
What, though, was really going on underneath my departed fingernail back then?
Turns out, the skin under our fingernails isn’t much different to the skin on any other part of the body (but I swear on my 10-year-old self that it looked strange). Unlike the rest of our skin, however, the skin under our fingernails adheres to the bottom of the nail and is chock-full of nerves to provide our hands with the extra sensation needed to perform day-to-day tasks. “For the most part, this skin is very sensitive because of the abundance of nerve endings we need there in order to help us with touch,” explains dermatologist Anthony Rossi.
While this is useful most of the time, trauma to this area is extremely painful, which is a good reason to avoid slamming your thumb in — to pull a random example out of thin air — a car door. Extra nerves aren’t the only reason that the skin underneath your nails are more prone to pain, though — that skin is also often affected by an abundance of pressure after being injured. “Classically, if we hit our finger with a hammer, it bleeds underneath the nail,” primary care physician Marc Leavey explains. “Then, that blood expands into this encapsulated place where there’s really no room for anything to expand.”
The result? Intense, throbbing pain.
Now, the best way to relieve this pressure is to somehow create an opening in the nail itself—something that can be achieved, as Leavey says, with a red-hot paper clip. Two things here: 1) We don’t endorse trying this technique at home; and 2) do not watch the below video if you find the sight of a literal fountain of blood upsetting.
Well, that was gross. But let’s bravely continue onward…
While the skin below your nails isn’t anything out of the ordinary, the bacteria that makes a home down there certainly is. According to one study, while other areas of the hand house hundreds (sometimes thousands) of bacteria, the area underneath our fingernails yields hundreds of thousands of bacteria per fingertip (*faints because fingers are currently in mouth, then returns to chair, pale-faced*). According to these researchers, this happens because the space between the skin and the nail provides both the physical protection and moisture necessary to create the perfect environment for bacterial growth. The space is also near impervious to our best means of killing germs ― soap.
With all of this in mind, do your best to clean the parts you can reach — especially if you’re one of the 23 percent of men who admit to trimming their nails by biting them. You really don’t want that bacterial orgy moving from your fingernails to your mouth.