How Hair Coloring Works

hair coloring
Coloring your hair is one way to get a new look. SrdjanPav / Getty Images

For a long time, hair coloring has been serious business! For example, would-be heroes of ancient Greece used harsh soaps and bleaches to lighten and redden their hair to the color that was identified with honor and courage. First-century Romans preferred dark hair, which was made so by a dye concocted from boiled walnuts and leeks.

Today, hair color remains hot, with a booming 75 percent of American women reportedly coloring their hair. (In 1950, only about 7 percent of American women colored their hair. And when they did, they did it to cover gray with their natural color and usually didn't want anyone to know they'd done it!) Women have also decided that blondes don't necessarily "have more fun!" Red is currently the most requested color at beauty salons. And women aren't alone...


Men increasingly cover gray or, following the female lead, completely change their look. Men's home hair-color sales reached $113.5 million last year, a 50 percent increase in just five years. The selection of coloring products and techniques is mind-boggling. Home coloring is less expensive -- ranging from about $4 to $10 per coloring (unless you have so much hair you need two packages!) -- than a trip to the salon, which, depending upon your hair length, color and the method used, can cost $50 and up.

In this article, we'll tackle the most important questions about hair coloring:

  • When should I go to a professional and when is a home job all right?
  • What formula and color should I choose and how will my hair react? And...
  • What if I really mess things up and end up looking like the neighbor's calico cat?

Don't worry -- we'll fill you in on how to prevent blunders as well as how to deal with them when they occur.

What Exactly Is Hair?

Typical mammalian hair consists of the shaft, protruding above the skin, and the root, which is sunk in a follicle, or pit, beneath the skin surface. Except for a few growing cells at the base of the root, the hair is dead tissue and is composed of keratin and related proteins. The hair follicle is a tubelike pocket of the epidermis, (see How Skin Works) that encloses a small section of the dermis at its base. Human hair is formed by rapid divisions of cells at the base of the follicle. As the cells are pushed upward from the follicle's base, they harden and undergo pigmentation.

The hair on our scalps and in our eyebrows and eyelashes are different from other bodily hairs. The hair on our heads grows a healthy .5 inch per month, and long scalp hairs have an average life of 3 to 5 years. Most of us have between 100,000 and 150,000 hairs on our heads!


There are two kinds of melanin found in the hair: eumelanin (the most common and responsible for hair shades from brown to black) and phaeomelanin (responsible for yellowish-blond, ginger and red colors). Absence of pigment produces white/gray hair. Before any permanent color can be deposited into the hair shaft, the cuticle, or outer layer, must be opened. The insoluble formula then reacts with the cortex to deposit or remove the color.

Ingredients in Hair Color

Until the early 1900s, hair coloring was made from a wide range of herbal and natural dyes. Flying in the face of other chemists who found the development of hair coloring trivial and unworthy of their time, French chemist Eugene Schuller created the first safe commercial hair coloring in 1909. His invention was based on a new chemical, paraphenylenediamine, and provided the foundation of his company, the French Harmless Hair Dye Company. A year later, the name was changed to one that is more familiar today -- L'Oreal. L'Oreal, one of the hair product giants, has grown steadily over the years; the company credits advanced and applied research of new product development and expansion into markets around the world with its global success.

The two main chemical ingredients involved in any coloring process that lasts longer than 12 shampoos are:


  • Hydrogen peroxide (also known as the developer or oxidizing agent) -- This ingredient, in varying forms and strengths, helps initiate the color-forming process and creates longer-lasting color. The larger the volume of the developer, the greater the amount of sulfur is removed from the hair. Loss of sulfur causes hair to harden and lose weight. This is why, for the majority of hair coloring, the developer is maintained at 30% volume or less.
  • Ammonia -- This alkaline allows for lightening by acting as a catalyst when the permanent hair color comes together with the peroxide. Like all alkalines, ammonia tends to separate the cuticle and allow the hair color to penetrate the cortex of the hair.

In addition, various types of alcohols, which can also dry the hair, are present in most hair color. (Check out this official ingredient list for a hair color formula.)

Hair Coloring Products

The good news is that most hair color products today have nicer smells than the tell-tale rotten-egg odor that once accompanied permanents or hair coloring. And most color can be applied easily: some to wet hair, others to dry hair, worked into a shampoo-like lather, left to process (some formulas call for covering with a plastic cap during processing; others do not) and then rinsed and conditioned.

The down side is still that chemicals in hair coloring can be harsh and harmful to your hair if you don't know what you're doing or if you color or perm too often. How peroxide and ammonia react with your hair is directly related to the level and kind of product you're using. Here are basic descriptions of the three major hair coloring product levels used by Clairol, L'oreal and others:


  • Level 1, semi-permanent color -- This product adds color without changing natural color dramatically. The hair color contains tiny color molecules that enter the hair's cuticle, or outer layer, and go into your hair's cortex. They don't interact with your natural pigments. And since the molecules are small, they eventually exit the hair shaft after several shampoos, leaving the hair as it was before treatment. This level generally lasts for 6 to 12 shampoos, covers up to 50 percent gray, enhances your natural color and leaves no roots. This hair coloring won't lighten your hair color because it contains no ammonia or peroxide.
  • Level 2, demi-permanent color -- This product level lasts longer, through 24 to 26 shampoos. In this process, pre-color molecules penetrate the cuticle and enter the cortex where they then partner to create medium-sized color molecules. Their larger size means they take longer to wash out. These products do not contain ammonia so the natural pigment can't be lightened. However, it contains a small amount of peroxide, which allows for a subtle, but noticeable, color enhancement. It also blends and covers gray. (Both semi- and demi-permanent colors can become permanent on permed or already-colored hair!)
  • Level 3, permanent color -- This is what you need for a more significant color change (to go from black to blond, you'll still need to go with a process called double process blonding and it'd be wise to get this it done professionally). In this level, both ammonia and peroxide are used. Tiny molecules enter all the way into the cortex, where they react and expand to a size that cannot be washed out. Your hair actually has to grow out over time. This product acts to lighten the hair's natural pigment to form a new base and then to add a new permanent color. The end result is a combination of your natural hair pigment and the new shade you chose. That means the color may appear different on you than on someone else using the same color. (That's why the "strand test" is so important -- more about that later.) Regular touch-ups of 4 to 6 weeks are generally needed to eliminate roots -- hair with your natural color growing at half an inch per month from your scalp.

There are also hair coloring products known as "special effect" hair colors. These are the kits you buy to add highlights or streaks to your hair. They are available in varying strengths. Some are for adding highlights to natural, uncolored hair while others are made for adding highlights to already-colored hair. Double process hair color, or bleaching and toning to achieve drastic color changes, falls into this category. Most professionals recommend you don't try this one at home unless you're really adventurous and love to experiment! Newer products on the market include color-enhancing shampoos and mousses and shampoos that keep your color vivid longer.

Now that we've reviewed the different product levels used in hair coloring, let's look at what actually happens to your hair. For example, if you're blonde and are going darker -- to brown -- permanent hair color uses the interaction between the ammonia and the peroxide to create a new color base in your hair shafts. If you go in the opposite direction -- from black or brown to blonde -- the hair goes through an additional step. First, bleach is used to strip the color from the hair. Then the ammonia-peroxide reaction creates the new color and deposits it in the hair shaft. If you use a semi-permanent color, the hair is coated with color, rather than deposited into the hair shaft.

Choosing the Right Hair Color and Product

Choosing a new hair color isn't as simple as finding a color you like on a box in the drugstore. You need to make this choice based on an analysis of your natural hair color, eye color and skin tone. First, let's review the basic "laws" of color. Color, as we see it, is actually the reflection of light off of the colored pigments in the hair shaft. It's sort of like the color prisms you saw in elementary school: it fractured light into distinctive colors you could see. This is what happens with hair color except that you're adding or subtracting colors to change from one color to another or to change the undertones.

A shade of color is made up of different combinations of reflections off the pigments. That's why hair color -- both natural and dyed -- looks different under fluorescent lights and in natural sunlight. Color levels are the degrees of lightness or darkness of a color seen by the eye. Hair color is assigned a level number from 1 to 10, with 10 being the lightest and 1 being black. Black reflects very little light and the lightest shades of blonde reflect the greatest amount of light. A colorist would say that a level 10 blonde is two steps lighter than a level 8 blonde.


Look at a color wheel or chart: Suppose you want to lighten your hair color. When hair is lightened, it produces warm, or yellow-red, undertones. Remember from school that mixing yellow and red produces orange -- not generally the desired hair color! Refer to the wheel to cancel out some of the orange tone but leave enough to keep the warm tones. The best hair colors for you if you have warm skin undertones (ivory, peachy, golden brown, creamy beige, cafe au lait, tawny, coppery, deep golden brown) and blue, blue-green hazel, green, topaz, amber or coffeebean colored eyes, are golden with red highlights, golden brown, honey brown, chestnut, copper and mahogany. Cool tones are blue-red. If your skin has rosy pink, rosy beige, dark olive, dark brown or ebony tones and your eyes are light blue, gray-blue, deep blue, deep green, brown or black, your best hair color options are plum and burgundy highlights, ash and platinum blonde, brown, dark brown, black, slate, salt and pepper and pure white.

Experts say you also can't miss if you return your hair to its color when you were 12 years old.

Your choice of hair coloring product depends on what you're trying to accomplish and how long you want your color to last. Most women start with a lower commitment level and move up to a higher level over time. If you're seeing more gray or your hair coloring isn't covering gray as well as it did, you might need to move to a higher-level product. Level 3 is the only kind of product that can completely and permanently cover any amount of gray.

The all-important strand test (always explained in home coloring packages) will ensure that you've chosen the right color -- and product -- and will give you a chance to change your mind. It works like this:

  • Mix one teaspoon of color and one teaspoon of developer (peroxide) in a glass bowl.
  • Apply the mixture to the roots or ends to determine the outcome. You can protect the test strand from the other hair by wrapping a piece of tin foil around the strand and securing it with a clip.
  • Time the process according to package directions, then rinse and dry the strand.
  • Look at it in different types of light to see if you like it.


What Can I Do About Gray Hair?

This woman had dark hair when the day started.

No, it's not your imagination. Some gray hairs -- especially coarse hairs, prematurely gray hairs and gray hairs around the temples and hairlines -- are especially resistant to color or quicker to lose color than other gray hairs. Try the following suggestions:

  • Apply color to gray areas first. (This gives resistant gray hairs more time to absorb color.)
  • Leave color on longer. (Adjust your timing and try it first in the strand test. Grays could take up to 45 minutes to color.)
  • Increase your hair color level. (If your grays still show up even after you've adjusted the timing on your semi- or demi-permanent color, you might consider going up a level.)

Science is also searching for a better solution to gray hair. Cancer researchers learned that liposomes, substances that deliver a drug into the body, can be used to deposit melanin, the pigment that gives hair its color, inside follicles and color hair from the roots up. If further research proves successful, products could be available in the next 10 years, they predict. On another front, after 30 years of research, L'oreal laboratories have developed a precursor molecule for melanin, dihydroxyl-5.6-indole, which enables the natural process of hair pigmentation to take place biologically through a slow oxydization process. With the right proportions, everyone could get back their own natural hair color! Researchers are using this new chemical to come up with a new way to enhance hair color or cover gray.



What Kind of Hair Color Do Men Use?

Everybody is familiar with progressive hair dyes for men -- products that build up to the desired color upon repeated use. There has been some question about the use of lead acetate as the developer in these products. (Some researchers worry about the danger of lead contamination to users and their children through hair and hands.) Professional colorists say they never use products containing leads because heads colored with these dyes can experience scalp burn when a conventional hair dye is used later. They say a special product must be used to remove all lead from the hair before traditional coloring.

On the other hand, manufacturers of Grecian Formula, GreyRemover and other progressive dyes say their products are safe because they contain small amounts of lead acetate (about 0.6 percent) -- amounts so small they can't be absorbed by the body if applied to a healthy scalp. The U.S. Food and Drug Administration approves the use of lead acetate in these small concentrations. So, educate yourself. Read the box carefully and if you have a question, call the company and/or a professional colorist. Or, you can do what many men are already doing: switch to women's hair color, which contains no lead acetate and comes in a much wider selection of products.


One of the newest trends among (mostly young) men is tipping, in which just the tops of their short, spiky hair strands are bleached or dyed (a la George Clooney and Ricky Martin) while the roots are left long and uncolored. L'oreal's new Feria for Men offers colors ranging from "goth black" to the most popular shade, "platinum blond." (Many colorists say they prefer working on guys because, if the color isn't quite right, the guys will often just tell them to shave it all off! Not likely with women!) Hair professionals are reporting that older men are getting that gray "erased" more and more often, citing the desire to remain viable in the ever-younger job market.

Colored Hair Care and Tips

Color treated hair has special needs. Follow these tips to keep your hair looking great:

  • Use a shampoo created especially for color-treated hair (Revlon, L'oreal, Aveda and Clairol all make them)
  • Wear hats or hair products with sunscreens to prevent your color from fading and drying in the sun
  • Dampen your hair with bottled spring water before getting into a chlorine pool (it will help dilute the chlorine)
  • Condition regularly
  • Don't brush hair when wet -- use a wide-toothed comb
  • Blot your hair dry -- don't wrap it or roughly dry it with a towel
  • Avoid overdrying -- blow dry until hair is almost, but not entirely, dry

When Should I Go to a Professional?

Technology has improved home hair coloring products, which also contain packets of deep conditioning lotion to prevent drying after coloring. So you can probably do a pretty good job at home on your own. However, there are times when it pays to see a professional colorist. For example:


  • You want to lighten or darken your hair more than three shades
  • You've colored your own hair and it's a disaster
  • Your hair is permed or damaged
  • You have never colored your hair and want a major change

How can I find a good colorist?

Your best bet is probably recommendations from people whose hair you admire. And don't be afraid to ask a lot of questions the next time you go for a hair cut. (Increasingly, there are hair stylists who have concentrated their training on hair coloring. This couldn't hurt!)

Troubleshooting Tips

If you still have questions, check the list of common queries received by stylist/colorist Robert Craig:

  • Getting rid of color stains on skin -- Baby wipes work well, but try to avoid getting color on the skin to begin with and make sure to wipe excess from the ears and hairline before it has time to stain.
  • Coloring during pregnancy -- Some doctors advise their patients to avoid any kind of chemical service during pregnancy. While there's little concrete evidence that coloring during pregnancy is medically harmful, you should make your decision after talking with your doctor and your colorist. Most professionals say you should do what makes you most comfortable. (By the way, pregnancy may affect hair growth, loss, condition and even the amount of curl up to a year after birth.)
  • Color fading due to chlorine -- If your local water contains a high amount of chlorine, you might consider getting a filter for your shower. Chlorine can strip color out of hair and make it very difficult to re-color.
  • Going back to natural color -- To avoid the two-tone effect of letting your color just grow out, have a professional use a similar formula with a highlighting method. In three to four visits, you will be able to stop coloring and not have an obvious line.

If the permanency of hair coloring worries you, you can still achieve a dramatic, fun change with some of the temporary, wash-out highlights you can spray on or paint on with mascara-like wands. These come in regular colors as well as wild-as-you-want-to-be colors! And even if you experience a hair coloring mishap at home, take comfort in the thought that even permanent hair color isn't really permanent. It will eventually grow out!

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