Quiz: Test Your Hair Coloring Know-How

About three out of four women dye their hair. Some do it to cover gray or to make a fashion statement. Some just want a change.

Permanent hair color causes more damage to hair than other types of dye. It chemically changes your hair, weakening the shaft and making it dry and brittle.

Protect your hair by using shampoo and conditioner with silicone, an ingredient that can minimize damage.

Bleaching your hair gets rid of color, leaving it white or yellowish white. Bleaching can make your hair dry, brittle, and more fragile -- just like dyeing it can. But it shouldn't make it fall out.

When new hair grows in, it won't be affected by the bleach. So it will be healthy.

Coloring your hair more often may cause damage that can't be fixed, like split ends and dryness.

To keep your color, you only need to re-dye the roots that start to show. Hair grows about 0.3 mm to 0.4 mm per day. That means in four weeks you'll have just a little more than 1/3 of an inch of roots showing.

It's called "weathering" -- environmental damage that leads to dry, frazzled-looking hair.

To protect your hair, watch how often you swim in chlorine-treated pools or saltwater. Wash your hair less often. And keep your hair out of the sun. UV rays can make your color fade.

No way. Never use hair dye on your eyebrows or eyelashes. It can cause a serious reaction if you get it in your eye. That's why hair dyes are banned for eyebrows and eyelashes -- even in salons.

It looks fine if your eyebrows are a little lighter or darker than your hair. But if you want to darken them, try an eyebrow pencil, powder, or gel specifically made for eyebrows. You can also color your brows with a temporary tint that you apply like mascara.

Our skin becomes thinner as we get older. So if your hair is really dark, it can make you look pale. If your hair is really light, it can wash out your complexion.

For a natural look as you get older, some experts recommend that brunettes go one shade lighter than their base color and blondes go one shade darker.

Men want to look younger, too. About one in 10 men color their hair now. The number has gone up over the past 10 years -- especially with men 50 to 64.

All that bleaching, buffering, and conditioning involved with the coloring process -- not to mention the wide variety of colors and processes out there -- involves a lot of chemical action.

The best way to see if you're allergic is a patch test. That means dabbing a little bit of dye on the inside of your elbow or behind your ear and waiting two days. If you get a rash, you're allergic.

Mixing different products together at home can hurt your hair and your scalp. If you can't find the color you like in a box, leave it to a trained salon worker to mix up the perfect shade.

Henna -- a natural, semi-permanent dye made from the leaves and roots of the mignonette tree -- usually gives you a brown, orange-brown, or reddish-brown tint. Other ingredients can be added to it to make other colors, such as black and blue.

Lead acetate is found mainly in gradual (progressive) hair dyes, which are usually used by men to cover gray hair over a few weeks. It's classified as a "probable human carcinogen," based on animal lab tests.

Products that have lead acetate are banned in Europe and Canada. The FDA said they can be used safely if you follow the instructions carefully and keep them away from kids.

The pigment molecules in semi-permanent coloring are small enough to get inside the hairs, with some molecules going deeper than others. When you shampoo, the larger pigment molecules wash away first. That changes your color each time you wash your hair.

When you dye your hair, a little bit of chemical can get absorbed through your skin. But most research suggests that this small amount of dye won't hurt a developing baby.

Some pregnant women switch to highlights because it uses fewer chemicals. Or they use pure vegetable dyes, like henna. But if you color your hair yourself, be sure to leave the dye on for the shortest amount of time and work in a well-ventilated room.