HAIR-DYES (an overview)
Chemotherapy and Hair-dyes
Women have been dying hair since before the time of the Biblical character – Moses. The first recorded references to this custom relate to Henna obtained from the Egyptian privet Lawsonia Alba.
Simple Hair dyes have historically been manufactured by the infusion (boiling in water) of natural vegetation.
Other categories possess increasingly complex chemical formulae which may change the physical structure of the hairshaft.
Modern Hair dyes can produce wonderful results, but some involve sophisticated chemicals which are capable of inducing: hair damage, toxaemia, or localised contact dermatitis in certain persons. Some types of hair dyes are currently thought to be linked to bladder cancer.
Hair dyes may be classified as:
Vegetable dyes: If pure are extracted from plants e.g. Saffron and Camomile, Privet, Black Myrtle leaves, Poppy heads, Green Walnuts, Ilex roots. Most vegetable dyes will wash out of the hair.
Henna however is a ‘permanent dye’ (the molecules are small enough to enter the cortex of the hairshaft) with the colour being oxidised by atmospheric oxygen. Henna may change the feel and lustre of hair.
Pure Vegetable dyes are basically harmless and do not require allergy tests. It is unlikely that any adverse skin reaction or hairshaft damage would result from their use. Egyptian (Vegetable) Henna however can, in some people, make the hairshafts seem dry and lustreless. This is not injurious. This form of henna is used in some shampoos e.g. to provide auburn highlights.
Camomile is another vegetable dye. The active ingredient is Apigenin (tri-hydroxyflavone). It is obtained from dried flowers of the Camomile plant. It coats the hairshaft adding a yellowish hue.
N.B. Readers should be aware that some ‘vegetable’ dyes may contain permanent oxidation dye ingredients which makes the product potentially harmful to certain persons. Please therefore read and understand the ingredients content before use.
Tunisian Henna where available is not a vegetable dye as it contains metallic salts and is classed as an inorganic dye.
Inorganic dyes: include hair colour restorers, sulphide and reduction dyes based on metallic salts (lead copper silver and iron). These dyes produce permanent colour changes.
Permanent waving the hair may be contraindicated because the combination of chemicals thus introduced may lead to rapid hairshaft destruction at scalp level.
Synthetic organic dyes are based on coal tar products. they include:
1) Temporary dyes such as Cationic dyes (e.g. Methyl violet) and Anionic dyes (or Azo dyes as in water based rinses). These dyes will wash out of hair.
2) Semi-permanent dyes: mixtures of nitro dyes and anthraquinones. These dyes produce red yellow and blue colourings. These dyes wash out of hair after 6-8 shampoos.
3) Permanent oxidation dyes (oxidation dyes) known as ‘para’ dyes. They require an oxidising agent e.g. hydrogen peroxide to function. These dyes include:
• para-phenylenediamine (black)
• para-toluenediamine (brown)
• ortho-phenylenediamine (Brown)
• para-aminophenol (reddish brown)
• ortho-aminophenol (light brown).
These dyes require allergy tests because moderate and severe skin reactions even toxaemia may result from injudicious applications.
Colours may fade with strong sunlight.
Hairshafts so treated will require special care when subjected to permanent wave processing.
The process may change the feel of hair.
Tinted hairshafts may be more vulnerable to breakage.
4) Quasi-permanent dyes are a mixture of semi-permanent and permanent oxidation dyes. The semi-permanent ingredient will wash out. Allergy testing is not always considered necessary, but is in the author’s opinion a wise precaution.
© Prof B Stevens FTTS
The Trichological Society