US A team of researchers has developed a hair dye made from a synthetic version of melanin,the natural pigment that gives human skin,hair and eyes their colour.Traditionally,high concentrations of toxic metals (copper and iron)and strong oxidants were required to use synthetic melanin to dye hair.However,scientists at Northwestern University,US,found that they could substitute mild heat and a small amount of ammonium hydroxide for the heavy metals and strong oxidants used in previous formulas.
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