Transition metals in Cosmetics
In hair chemistry hair fibres are commonly used as cosmetics. Hair fibres are composed of approximately 85 % of the complex protein keratin, with some 7 % of associated water. The other principal constituents are lipids 3 %, and pigment 2 %. This last component is melanin, derived in biosynthesis from the amino acid tyrosine. Also present are trace amounts of many metals such as aluminium, calcium, and many transition metals such as iron, manganese, magnesium, copper, chromium and zinc, the last in a fairly high concentration of 22 mg per 100 g of hair. (butler, 2000)
Nickel as one of the transition metals is used in cosmetics as skin sentisizer. To behave as a skin sentisizer a substance must first penetrate the stratum corneum, partition into the epidermis, and react with endogenous proteins to form a hapten-carrier conjugate
Such substances according to ( leyden and rawlings,2002 ) will therefore normally be of low molecular weight ( normally