Hair colorants

Hair coloring


Hair coloring is a process used to color human hair. It is used for a variety of purposes; most commonly to return gray hair to its previous color, to change hair color to a shade regarded as more desirable, or to return hair to its original color after chemicals (e.g. tints, relaxers, sun bleaching) have discolored it.

Types of hair color

Hair coloring products are typically categorized based on the length of time they effect the colored hair. The four most common classifications are 'temporary', 'semi-permanent', 'demi-permanent' (sometimes called 'deposit only'), and permanent. Hair lightening products such as bleaches could be regarded as a sub-set of permanent hair coloring products, as their effects are permanent.

Temporary hair color

The pigment molecules in temporary hair color are large and, therefore, do not penetrate the cuticle layer, allowing only a coating action that may be removed by shampooing.

Acid dyes are used to coat the surface of hair, since acid dyes have a low affinity to hair, thus can be removed after a shampoo. The penetration and color strength of temporary hair color can usually be improved by applying a bleaching prior to the application of the hair color. Temporary hair color is available in various product forms including rinses, shampoos, gels, sprays, foams and others. This type of hair color is typically used to give brighter, more vibrant shades or colors such as orange or red, that may be difficult to achieve with semi-permanent and permanent hair color. Temporary color is also used by some teens for events at school and Halloween. This phenomenon is because temporary hair colorants do not penetrate the hair shaft itself. Instead, these dye particles remain adsorb (closely adherent) to the hair shaft and can be easily removed with a single shampooing. However, even temporary hair coloring agents can persist if the user's hair is excessively dry or damaged, conditions that allow for migration of the dye from the exterior to the interior of the hair shaft. While temporary hair color products hold a lesser market than semi-permanent and permanent agents, they have value in that they can be easily and quickly removed without bleaching or application of a different colouring product.

Semipermanent hair colour

Formulated to deposit colour on the hair shaft without lightening it. This formula has smaller molecules than those of temporary tinting formulas, and is therefore able to partially penetrate the hair shaft. It has no developer, but may be used with heat for deeper penetration. It also lasts longer than temporary hair color, keeping mostly intact up to 4-5 shampoos. They are great for hair that is damaged and fragile. Semi hair color has no Ammonia.

'Demi Permanent' hair color

Companies like Compagnia Del Colore from Italy have found a way to change the color pigment molecules to be smaller than that of semi permanent hair color but still larger than permanent hair color molecules. This is done by mixing permanent hair color with low volume (usually a 7 volume developer) that blows off the ammonia from the permanent tube and deposits colour molecules only into the hair shaft. A demi is a gentler than permanent color used whenever you want to deposit color without lifting the natural pigment but with the penetration being more than semi permanent color but less than permanent, the results last longer than semi but shorter than permanent hair color. Since they are more gentle than permanent hair color, they are great for tint-backs and colorpriming. They are also great for toning pre-lightened hair. Because there is no lifting of natural hair colour, they are not as effective on dark hair, due to the over-powering colour already existing in the hair.

Permanent color

All "permanent" haircolor products and lighteners contain both a developer, or oxidizing agent, and an alkalizing ingredient as part of their ammonia or an ammonia substitute. The purpose of this is to:

  • raise the cuticle of the hair fiber so the tint can penetrate,
  • facilitate the formation of tints within the hair fiber,
  • bring about the lightening action of peroxide.

When the tint containing the alkalizing ingredient is combined with the developer (usually hydrogen peroxide), the peroxide becomes alkaline and diffuses through the hair fiber, entering the cortex, where the melanin is located. The lightening occurs when the alkaline peroxide breaks up the melanin and replaces it with new color.

Permanent Color is the best choice for grey hair coverage. It has a oxidizing dye that also uses ammonia and peroxide to lift and deposit the new color, going deep into the hair shaft. The use of ammonia opens the cuticle of the hair to allow the color pigments to penetrate deep into the hair shaft.

Hair lighteners and bleaches

"Hair lightening," referred to as "bleaching" or "decolorizing," is a chemical process involving the diffusion of the natural color pigment or artificial color from the hair plus the raising of the cuticle making the hair more porous. This process is central to both permanent hair color and hair lighteners.

Application techniques

Typically, hair colouring is used in one of two ways:

  1. One colour is applied to all hair on the head, to produce a uniform color effect, or
  2. Several individual color preparations are applied to selected sections of the hair, to produce streaks or gradations of color.

The latter technique can be used to create many different effects, from subtle highlights acquired during a day at the beach, to more dramatic looks, such as bold, chunky highlights. The terms most commonly used to describe these techniques are:

  • Highlighting, where sections of hair are treated with lighteners, usually to create blond streaks.
  • Lowlighting, where sections of hair are treated with darker hair colour.
  • Foils, where pieces of foil or plastic film is used to separate off the hair to be colored; this is especially nice 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 colour contained.

Both application techniques can be used with either colour treatments that range from temporary to permanent.

Exotic hair colorants

While the majority of hair colouring products are designed to produce natural-looking hair color shades (typically blond, red, brown or black), 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). (By contrast, regular hair colors are sold in drugstores and department stores and through professional beauty suppliers.) Many exotic color shades are blacklight reactive, which suggests that the wearers typically want their hair color to show up under nightclub lighting.

The chemical formulae of exotic colored 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. Therefore, the majority with darker hair (medium brown to black) are advised to use a bleaching kit prior to tint application in order to get the full effect of the color. Some people with fair hair may benefit from prior bleaching as well, as the yellow undertones of blonde hair can make blue dye look green, and to make the hair porous to easily absorb the pigments into the hair shaft.

These colors are less permanent, being partially removed with each shampoo, and tend to "bleed" onto other fabric even when dry. Users should anticipate staining of light-colored pillows for a week or so after application.

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 dye 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 dye but can also arise after hours or even a day.

To help prevent (of rather, limit the extent of) 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 dye and applying it directly to the skin. If irritation develops, manufacturers recommend that the client not use the product. A skin patch test is advised before the use of every colouring 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, as similar chemicals are used in either setting.

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.

In the United States, there have been successful law suits against hairdressers who caused clients' hair to break off.

Skin discoloration

Many hair colors will color skin almost as well as they color hair. Skin and hair are made of the same type of keratinized protein. That means that drips, slips and extra hair tint around the hairline can result in patches of discolored skin. This is more common with the darker hair dyes and persons with dry skin.

This discoloration is temporary; it will disappear as the skin naturally renews itself and the top layer of skin is removed. This typically takes a few days or at most one week.

Unpredictable color results

In some cases, the hair color a person has after coloring their hair is not what they expected to get. In general, this is more likely to happen using at-home dyes, as professional colorists are more aware of what can realistically be achieved with tints and what will distort results. They also typically have a range of products available (such as toners) to correct unintended results before the client sees them.

Some of the things that can cause unintended results include:

  • Trying to lighten or darken hair more than 3 shades using at-home products
  • Coloring already-colored hair
  • Previous use of henna, which can react unpredictably with industrial dyes

In the event of unfortunate unintended results, an immediate visit to a professional hair colorist is generally recommended.

Health concerns

There is ongoing debate regarding more serious health consequences that may result from use of hair coloring.

Recent publications regarding the dangers of hair tints include:

  • An FDA study that found lead acetate (the active ingredient in gradual darkening products such as Grecian formula) to be potentially toxic. )
  • Articles that link the development of some forms of cancer (including leukemia, non-Hodgkin's lymphoma, bladder cancer, blood cancer, and multiple myeloma) with use of hair color
  • Death of Brain Cells-Some experts claim that hair bleach can kill brain cells (unsubstantiated; source of the "blonde jokes")

Alternatives to industrial tints

It has been recorded historically that ancient civilizations dyed their hair using plants. Some of the most well known are henna, indigo, Cassia obovata, senna, turmeric and amla. Others include katam, black walnut hulls, and leeks .

Presently, there are some companies that do sell alternate based dyes for people that are sensitive to PPD, a chemical found in most hair colors.

There are also said to be safer products that avoid the side-effects of most industrial tints. The safer alternatives generally contain fewer potentially toxic compounds or are plant based, and do also have temporary, semi-permanent and permanent options. However, these products typically do not last as long as industrial tints. Users should be cautioned that allergic reactions are possible even from these "natural" vegetable dyes.


Uses a mild, creamy developer of a lower volume (than other products of same or similar composition), including but not limited to the dye used in textiles, sunscreen, rubber, and/or certain medications. These are also termed "No-Lift Permanent" or "Deposit-Only". In general, there is no lift or lightening as there is no ammonia to act as a catalyst. With these colors you can add Red, Violet, or Blue tones, cover grey/white or go darker. These colors last 15-25 shampoos.


Formulated to deposit color on the hair shaft without lightening it. This formula has smaller molecules than those of temporary tinting formulas, and is therefore able to penetrate the hair shaft somewhat. Contain no developer or peroxide, and contain no ammonia. It is possible to cover graying shades of hair temporarily with this type of hair coloring, but be advised that it may wear off in 5-7 shampoos. In addition, note that hair products labeled as semi-permanent may contain the toxic compound P-Phenylenediamine or other such products found in traditional hair color.

Henna is a plant that is also used for ayurvedic hair coloring. The red dye is commonly used as a deposit-only hair color whose active component, lawsone, binds to keratin and is therefore semi-permanent, but it will wash out with time, generally a couple of months. While "natural" henna is generally a deep red-color, variations exist. These variations, however, usually contain ingredients from other plants and even synthetic dyes.

Using a plant-based color, specifically henna, can cause problems later when trying to do a perm and other permanent hair color. Many people have the misconception that discoloration can occur on hair that has been previously tinted with henna and that hennaed hair cannot be curled. This is untrue, as long as pure imported body art quality henna is used; whereas store-bought "boxed" henna is often mixed with harmful additives, which can cause damage or discoloring to hair. Although it may not be visible on darker hair, the staining from henna will remain for several months and may only show up when trying to lighten hair, and a definite orange tone will appear which will be impossible to remove.

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