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A woman with dyed pink hair. Hair coloring, or hair dyeing, is the practice of changing the color of the hair on humans' heads.The main reasons for this are cosmetic: to cover gray or white hair, to alter hair to create a specific look, to change a color to suit preference or to restore the original hair color after it has been discolored by hairdressing processes or sun bleaching.
Lawsone (2-hydroxy-1,4-naphthoquinone), also known as hennotannic acid, is a red-orange dye present in the leaves of the henna plant (Lawsonia inermis), for which it is named, as well as in the common walnut (Juglans regia) [5] and water hyacinth (Pontederia crassipes). [6]
It is a red-pink dye used for food coloring, cosmetics, hair coloring, pet products, and diverse industrial colorings. [ 2 ] [ 3 ] It is the disodium salt of 2,4,5,7-tetraiodo fluorescein . [ 2 ]
Because of the chemical nature of hair dye strippers, they are effective on both newly dyed hair and older dye. Note that this type of color correction is ineffective on hair lightened with hydrogen peroxide, as hair bleaching is an irreversible chemical reaction that oxidizes hair's melanin, effectively rendering it colorless. [3] Most color ...
Semi-permanent hair color cannot lighten hair. [23] Hair can only be lightened using chemical lighteners, such as bleach. Bleaching is always permanent because it removes the natural pigment. "Rinses" are a form of temporary hair color, usually applied to hair during a shampoo and washed out again the next time the hair is washed.
Which brings us to the research behind the effects of Red Dye No. 3. (It's controversial.) Both the cosmetic and food bans of Red Dye No. 3 are the result of a single study published in 1987 .