Hair Coloring / Pigmentation - Commonly Used Hair Dyes

Men and women have colored their hair as a form of self-expression dating back to ancient Greek, Roman, Indian, and Middle Eastern civilizations.¹ Some of the first hair colorants included ingredients such as cassia bark, leeks, leeches, charred eggs, and henna.¹ It wasn’t until 1907 when the first synthetic hair dye was developed by a French chemist named Eugene Schuller. Hair coloring is still a widely popular trend to this day.¹

What Causes Natural Hair Pigmentation?

Melanin is a natural pigment polymer, which contributes to human skin color and influences the degree of hair pigmentation.² Of the two types of melanin found in human hair follicles, eumelanin produces a blackish-brown color while pheomelanin produces a reddish-brown color.² The ratio of these two types of melanin contribute to different color variations.²

Melanocytes are the cells in the body that produce melanin. For every melanocyte there are five keratinocytes in the hair bulb that form a hair follicle melanin unit.² Hair pigmentation activity changes throughout the hair growth cycles (i.e. anagen, catagen, and telogen).² During anagen, the growth phase, melanogenesis is active. Melanogenesis halts in the catagen (transition) and telogen (resting) phases.²

Image 1: Hair Follicle Anatomy

How do Hair Dyes Change Hair Color?

The hair shaft is composed of the cuticle (the outermost layer), cortex, and the medulla (the innermost layer).³ Hair pigmentation through hair dyes is achieved through differing degrees of penetration from the hair cuticle into the medulla.⁴ There are several different types of hair dyes including:⁴

• Gradual
• Temporary
  • root touch-up sprays
  • mascara root touch-up wands
  • colored hair sprays
  • hair chalk
• Semi-permanent
• Demi-permanent
• Permanent
• Vegetable
  • Henna
• Bleaching
• Highlighting

The two most common types of hair dyes are:⁵

• Permanent dyes
• Demi-permanent dyes

Permanent dyes

Permanent dyes penetrate and deposit within the cortex, whereas demi-permanent dyes coat the cuticle and eventually fade with subsequent washes.⁵ The pH of a dye determines its penetration capabilities.^4,5 Alkalizing agents, such as ammonia or ethanolamine, help the pigment to infiltrate the cuticle to reach the cortex.^4,5 These agents damage the cuticle’s structural integrity overtime and may result in dry brittle hair.⁶ 

Primary intermediates, developers, and couplers are also used in permanent hair dyes to create a reaction resulting in color deposition in the cortex.⁷ A primary intermediate is a dye precursor that reacts with a developer.⁷ This product will then react with a coupler.⁷  Primary intermediates and couplers will cause the dye formation reaction after the hairs are bleached.^5,8 The oxidation reaction that occurs allows primary intermediates such as para-phenylenediamine (PPD), para-toluenediamine, or para-aminophenol, to infiltrate the cortex.⁵ The most common couplers used are resorcinol and m-aminophenols.⁸ Resorcinol is thought to reduce the production of melanin by inhibiting tyrosinase activity.⁸

Demi-permanent dyes

Demi-permanent hair dyes are less damaging than permanent hair dyes since they do not contain ammonia or ethanolamine, and do not penetrate and cause damage to the cortex as they only cling to the hair cuticle.⁵ However, like permanent dyes, they do contain hydrogen peroxide (at lower concentrations), resorcinol, and para-dyes.⁵ Since these dyes only accumulate on the cuticle, they are not as effective for dying gray or white hair and will not lighten the hair color.⁵ These dyes are more effective for achieving a darker pigment because there is less hydrogen peroxide or bleach needed to achieve lighter hair colors. Demi-permanent hair color pigmentation may fade after 10-15 washes.^4,5

Henna hair dyes

In contrast to the previously discussed chemically-based products, henna-based hair dyes are emerging as the most popular natural hair dying trends. Henna hair dyes can last about 4-6 weeks depending on how frequent the hair is washed. Henna is derived from the dried and powdered leaf of Lawsonia inermis, commonly known as red henna.⁵ Most henna dyes are vegetable dyes and may contain PPD to produce a darker pigment.⁴ As mentioned earlier, PPD can be used in permanent dyes as a primary intermediate.⁵ Many henna products on the market may contain PPD, which is a popular skin irritant.^4,9 Lawsone, another active ingredient in henna dye, may cause irritation to the skin.^4,5 Due to its highly sensitizing nature, a patch test may be recommended before using henna hair dyes.⁹

What Causes Hair to Turn Gray?

Genetic and environmental factors can contribute to graying hair, resulting in decreased melanocyte production in the hair follicle through oxidative stress.² Unfortunately, most hair dyes will cause oxidative damage.⁸ As a result, constant and early hair dying may promote premature hair graying.^2,5,8

Other potential causes of premature graying include emotional stress, nutritional deficiencies (specifically B5, B12, protein, copper, iron, zinc), progeroid syndromes (a group of rare genetic disorders that cause premature aging), chemotherapeutic drugs, antimalarial drugs, decreased thyroid hormones, vitiligo, and smoking.²

Ways to reverse graying hair

Despite the lack of clinical evidence, Polygonum multiflorum, calcium pantothenate, and para amino benzoic acid (PABA) are supplements that may potentially reverse premature graying.

Polygonum multiflorum

Polygonum multiflorum radix has traditionally been used in Chinese medicine to darken hair and promote hair growth.¹⁰ Unfortunately, efficacy of this herb has not been tested in human clinical trials.  

A study performed using a raw crude extract of Polygonum multiflorum on mice was more effective than its processed formulation in reversing gray hair.¹¹ The heating/extraction process involved may affect and diminish the chemical constituents in raw crude plant.¹¹ Upregulation of melanin production (POMC gene, α-MSH, MC1R, and TYR proteins) was observed after topical and oral administration of Polygonum multiflorum.¹¹

Another study applied Polygonum multiflorum root extract to human hair cells, SKMEL-28 melanoma cells, zebrafish embryos, and zebrafish larvae, which stimulated melanin synthesis.¹⁰

L’Oréal’s research and innovation team studied the effects of a Polygonum multiflorum radix extract on human melanocytes in vitro and on hair follicle pigmentation ex vivo.¹² The extract inhibits the generation of reactive oxygen species, preserves intracellular levels of glutathione (an important antioxidant that helps combat oxidative stress), and protects human primary foreskin melanocytes against oxidative stress-induced cell death after hydrogen peroxide exposure.¹² A higher melanin content was seen in the ex vivo follicles culture after 4 days.¹²

These preliminary studies show promising results. However, more research is needed on this botanical and its effects on hair pigmentation.

Calcium pantothenate

There is limited evidence for the use of calcium pantothenate to evaluate the use for gray hair repigmentation.¹³ Two individuals taking 200 mg of calcium pantothenate experienced some hair repigmentation after one month of supplementation (757 and 1069 grey hairs were counted to have converted into black hairs).¹³ A 3-year prospective cohort study involving 7 females found that the use of 100 mg or 200 mg of calcium pantothenate caused 28% of the patients to experience repigmentation after 3 months.¹³ However, pantothenic acid deficiency is rare in developing countries, and large doses surpassing 5 g/day may cause diarrhea and abdominal pain.¹³ Therefore, caution should be taken and more studies are needed to further evaluate the effects of calcium pantothenate.

Para amino benzoic acid (PABA)

The use of 200 mg PABA daily on 50 patients resulted in subjectively darker hair pigmentation in all patients after 2 months.^13,14 One prospective study evaluated using both calcium pantothenate and PABA on 27 participants with pre-mature graying.¹³ After patients supplemented with 100 mg of calcium pantothenate and 200 mg of PABA daily, 6% experienced a definite hair color change and 21% experienced a slight hair color change after 8 months of treatment.¹³ After discontinuing supplementation, the hair reverted back to gray.¹³

Practical Tips

• Ask patients what type of hair dye they are using to understand how it may be affecting the quality of their hair due to its level of penetration.
• Educate patients on the effects and potential risks of different hair dyes.
• If a patient comes in inquiring about methods to reverse premature hair graying, inform them of the lack of research and potential supplements being studied: Polygonum multiflorum, Calcium pantothenate, and Para amino benzoic acid (PABA).