The dyes are cosmetics with the aim of giving a different color than the natural.
The hair dye can be of vegetable, mineral or synthetic nature.
The vegetable dyes are obtained by pressing or extraction from flowers, branches or fruits of certain plants. They do not involve any allergic factor even if they have a wide choice of colors.
These dyes are attached to the hair by means of hydrogen bonds (very weak link), they are not very resistant to washing.
These include the 'Henna . It is a shrub of Asian origin. The leaves and stem contain a dye called Lawsone , a chemical that has a naftochinolone . The Lawson and soluble in alcohol for the presence of ' phenolic OH, and in alcohol and glycerin. Henna is added water-alcohol solution or hydroglycerin, to enable fixing of the dye, a slightly acidic pH. Henna provides a color dark auburn hair carrot red hair and very light or white.
is also very common chamomile, which contains flavonoids , very faint yellow colors that give the blond highlights. Chamomile also contains chamazulene, a substance that can carry a weak anti-inflammatory and anti-inflammatory nature.
The mineral dyes contain lead acetate or silver nitrate, and minerals are the only ones allowed by law.
These do not give stable ties with keratin of the hair (hair), so the hair gets easily treated everything it touches (towels, sheets, etc.)..
L ' lead acetate on the hair is oxidized to rust, dark gray. The process is very slow and for this reason the substance is very suitable for coloring hair.
Its concentration should not exceed 2%, it is very toxic.
The silver nitrate brings brilliance and can also be used on eyelashes and eyebrows (it's dangerous but if it comes into contact with the eyes). Its concentration should not exceed 4%.
The synthetic dyes are the most popular. They are divided into temporary, that are resistant to a wash, semi-permanent, resistant to 5-10 washes, and permanent, resistant to more than 10 washes. The
temporary dyes containing azo dyes and anthraquinone. The semi-permanent instead of aromatic compounds.
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