What is earwax, and why do humans have it? --- Kate, Santa Clara, Calif.
Marshall Brain Answers:
Ear wax... kind of gross, like boogers, but a part of life for humans and lots of other mammals.
Ear wax is actually a specialized kind of sweat. Humans have two kinds of sweat - the mostly-water kind that we use for cooling, and the smelly, oily kind that we have in our underarms and a few other select spots around the body (see How Sweat Works). Apocrine sweat glands (the smelly kind) add protein and fats to the sweat. A modified form of these sweat glands is found in the ear canal, and its output is ear wax. Some people have drier, flaky ear wax, and others have wetter, oilier ear wax, depending on genetics.
As described on this page, about half of the weight of ear wax is made of dead skin cells. The rest is oils and proteins.
If you think about it, the ear canal is covered with skin but is not easy to reach. That means it is hard to clean the skin in the ear canal or to scratch it. Therefore, it is thought that ear wax helps to keep things out of the ear canal (including certain kinds of bacteria), helps to lubricate the ear canal, helps to keep the canal clean (by coating the canal and also trapping dirt), and helps to keep itching down (in the same way a layer of petroleum jelly can sometimes help stop itching).
One problem with ear wax is that it can build up in the ear canal. Sometimes it can completely plug the ear canal. This video shows how bad things can get, as they use a suction tube to remove chunks of ear wax from different ears:
See also: Wax Blockage In The Ear Image and Wax Blockage