Ever Wonder Why You Have Fingernails?

By Howard J. Bennett

The hand is one of the most amazing parts of the human body. You may not have studied this yet in school, but the human hand has something referred to as “opposable thumbs.” This means we can use our thumbs and fingers to grab and manipulate objects. Chimpanzees and other large primates have thumbs that resemble ours, but their thumbs are positioned in such a way that they can’t grab objects the way we do. This ability is essential for being able to make and use complex tools.

But what about fingernails? Although modern humans may take them for granted, fingernails are important for our day-to-day actions. They help us
dig, open things and even scratch an itch. Fingernails are made from a tough protein called keratin. (Primates aren’t the only animals that have found a use for keratin—hooves, horns and claws are also made from this substance.)

Keratin gives hair and the outer layer of skin its strength. The reason fingernails are tougher than hair and skin is because the keratin fibers that make up nails are more dense (packed together). Keratin is also insoluble, which means it repels water. That’s why you don’t swell up like a sponge when you go swimming or take a bath!

Here are some other interesting tidbits about fingernails.

Despite what you may hear, white spots in fingernails are not due to a calcium deficiency. Instead, they are caused by small injuries to the nail. Throughout the day, your fingernails get banged and squeezed in various ways. (Most of the time, you won’t notice when this occurs.) If you push on the end of a fingernail, it will bend like the type of flexible plastic that’s used to package certain kinds of canned soft drinks. If you bend and straighten this type of plastic, you may notice a white spot where the bend has occurred. This is similar to what happens to fingernails.

Biting your fingernails is one of the most common habits in people, especially kids. No one knows why it’s so tempting to chew on your fingernails, but parents have been bugging their kids to stop the behavior for centuries. What many parents may not know is that nail biting “runs in families.” That means if you bite your fingernails, there’s a good chance one of your parents did the same thing when they were kids. However, even if this is true, it’s still not a good idea to bite your nails. Doing so can damage the enamel of your teeth and may cause an infection in your finger.

If you bang your fingernail really hard, you may develop a hematoma (blood clot) under the nail. While this is not dangerous, it hurts like heck. If the hematoma is large, doctors may treat it by making a tiny hole in the nail to let the blood out. This relieves the pressure (and the pain) until the injury heals.

Of course, any article on fingernails would be incomplete without saying something about nail polish. The practice of decorating fingernails seems to date to the time of the Incas about 600 years ago. The smell of wet nail polish can give you a headache (especially if you’re male), but it’s not dangerous to use. However, repeatedly using nail polish may cause a person’s fingernails to turn a yellowish color.

© 2012 Howard J. Bennett. All Rights Reserved.
(First published in the Washington Post 4/8/12.)

For more KidsPost articles and lots of other cool stuff,
please visit Dr. B’s website at http://www.howardjbennett.com.