Permanent Hair Color

All "permanent" hair color products and lighteners contain a developer, or oxidizing agent, and an alkalizing agent (most often ammonia).
When the tint containing the alkalizing ingredient is combined with the developer cause a chemical reaction that swells the hair permitting the tint to enter the cortex, where the melanin is located. The melanin is lightened and subsumed by the new color. The ammonia swells the cuticle of the hair to allow the color pigments to penetrate deep into the hair shaft.
Permanent color is truly permanent and will not wash out, although it may fade. New hair growth in the hair's natural color will contrast with the colored section of the hair.
Permanent hair dyes can be removed by bleaching, or stripping with a color remover. In the case of striping hair color, this process will only be effective if the original hair color is lighter than the dyed result. Theoretically a color remover will return hair to its natural color if the hair has been color treated but this process is damaging to the hair.

Hair lighteners and bleaches
Bleaching, also referred to as hair lightening or decolorizing, is a chemical process involving the diffusion of natural color pigment or artificial color from hair. Hydrogen peroxide and ammonium hydroxide are frequently used. It has the side effect of raising of the cuticle, making the hair more porous.
Any color treatment to change to a lighter color requires bleaching. After bleaching, a light colored permanent or semi permanent dye or toner may be applied to the hair to further alter the color achieved by bleaching.
Application techniques
Hair color was traditionally applied to the hair as one overall color. The modern trend is to use several colors to produce streaks or gradations, either on top of the natural color or on top of a single base color. These are referred to as:
Highlighting, where sections of hair are treated with lighteners, usually to create blond streaks.
Lowlighting, where sections of hair are treated with darker hair color.
These can be applied by the following methods:
Foiling, where pieces of foil or plastic film are used to separate off the hair to be colored; especially when applying more than one color.
Cap, when a plastic cap is placed tight on the head and strands are pulled through with a hook.
Balayage, where hair color is painted directly onto sections of the hair with no foils used to keep the color contained.
All application techniques can be used with any type of color. For highlights, the hair will usually have to be bleached before coloring.

Alternative hair colorants

Hair and beard colored blue.
A minority of hair coloring products are designed to create hair colors not typically found in nature. These are available in almost any color imaginable, including green or fuchsia.
These dyes are typically sold in punk-themed stores (such as comic book and music stores), with brand names like "Beyond The Zone", "Splat", "Clairol Jazzing", "Manic Panic", "Special Effects", "Punky Colour", "Stargazer", "La Riche Directions". A permanent alternative in some colors (such as bold red and dark, inky purples and blues) are available from big haircare brands. Some alternative color shades are blacklight reactive, to show up under nightclub lighting.
The chemical formulae of alternative color dyes typically contain only tint, and have no developer. This means that they will only create the bright color of the packet if they are applied to light blond hair. People with darker hair (medium brown to black) will need to use a bleaching kit prior to tint application. Some people with fair hair may benefit from prior bleaching as well. Gold, yellow and orange undertones in hair that hasn't been lightened enough can adversely affect results, especially with pinks, blues, and greens. Although alternative colors are semi-permanent in the cases of some colors, such as blue and purple, it could take several months to fully wash the colour from bleached or prelightened hair.

Adverse effects of hair coloring
Hair coloring involves the use of chemicals capable of removing, replacing and/or covering up pigments naturally found inside the hair shaft. Use of these chemicals can result in a range of adverse effects, including temporary skin irritation and allergy, hair breakage, skin discoloration and unexpected hair color results.
Additionally, there is ongoing debate regarding more serious health consequences of hair color usage, including lead poisoning.


Skin irritation and allergy
In certain individuals, the use of hair coloring can result in allergic reaction and/or skin irritation.
Symptoms of these reactions can include redness, sores, itching, burning sensation and discomfort. If any of these symptoms occur, alert your hair colorist immediately so that they can remove the color. Symptoms will not always be present right at the application and processing of the tint but can also arise after hours or even a day.
To help prevent or limit allergic reactions, the majority of hair color products recommend that the client conduct a patch test before using the product. This involves mixing a small quantity of tint preparation and applying it directly to the skin for a period of 48 hours. If irritation develops, manufacturers recommend that the client not use the product. A skin patch test is advised before the use of every coloring process, since allergies can develop even after years of use with no reaction.
Adverse reactions can result from both at-home and salon hair coloring products, as similar chemicals are used in both settings .
In some cases, allergic reactions are caused by the aniline derivative and/or p-Phenylenediamine (PPD) found in permanent hair color.

Hair breakage
Hair that has been damaged by excessive exposure to chemicals is considered 'over-processed'. This results in dry, rough and fragile hair. In extreme cases, the hair can be so damaged that it breaks off entirely. This is especially true for Afro-Caribbean hair, especially if used in combination with relaxers. Treatments are available but the only real solution is to stop the use of chemicals until new hair grows and the damaged hair is cut off.
It is advised that colored hair be deep conditioned regularly, and washed and conditioned with gentle products specifically designed for color-treated hair. This will help keep the hair intact and minimize color fading.

Skin discoloration
Skin and fingernails are made of the same type of keratinized protein as hair. That means that drips, slips and extra hair tint around the hairline can result in patches of discolored skin. This is more common with darker hair colors and persons with dry absorbent skin.
This discoloration will disappear as the skin naturally renews itself and the top layer of skin is removed (typically takes a few days or at most a week). A good way to prevent dye discoloration is to put a thin layer of Vaseline or any oil-based preparation around the hairline. It is recommended that latex or nitrile gloves be worn to protect the hands.