School: Sidney high School

Grade: 11

Teacher: David Pysnik

Hobbies/Interests: Field hockey, reading and basketball.

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Question: Why does the sun darken your skin, but lighten your hair?

Answer: That is a great question! The answer has to do with melanin, a pigment that gives color to skin and hair. Special cells in the skin, called melanocytes, make two different types of melanin, eumelanin, which has a brown or black color, and pheomelanin, which is yellowish-red. How much of each kind of melanin we make determines the exact shade of our skin and hair color.

Most people have the same number of melanocytes, but some people’s melanocytes make more or less melanin than others. A few people cannot make any melanin and have white skin and hair (albinism).

Why do we even need this coloring? Melanin helps protect our skin and hair by filtering out potentially harmful ultraviolet (UV) radiation from the sun. When people with lighter skin are exposed to the sun, melanocytes make more melanin and the skin gets darker. This is a slow process, however. Skin burns if a person with lighter skin gets too much sun too fast. Red heads are particularly sensitive. People with darker skin (for example, African-Americans) make lots of melanin all the time so tend not to get sunburn or skin cancer.

Things work differently in our hair. UV radiation from the sun makes hair brittle (dry and fragile) and damages the melanin so that it loses its color. Because hair is no longer living, the melanin cannot be replaced.

So, tanned skin and bleached hair may be a sign that someone is spending too much time in the sun. Try to keep your skin light and your hair dark by wearing sunscreen and a hat!

Cool links for kids:
http://www.pbs.org/wgbh/nova/ice/chill.html
http://pubs.usgs.gov/gip/ice_age/
http://www.nrm.se/virtexhi/mammsaga/welcome.html.en
http://www.deq.state.mi.us/documents/deq-gsd-info-geology-BU4FB.pdf
http://museum.state.il.us/exhibits/ice_ages/
http://library.thinkquest.org/J001457/
http://www.priweb.org/mastodon/mastodon_home.html
http://geology.about.com/cs/rock_collecting/

Ask a Scientist appears Wednesdays. Questions are answered by faculty at Binghamton University. Teachers in the greater Binghamton area who wish to participate in the program are asked to write to Ask A Scientist, c/o Binghamton University, Office of Communications and Marketing, PO Box 6000, Binghamton, NY 13902-6000 or e-mail scientist@binghamton.edu.