Hair coloring systems delivering color with reduced fiber damage

The possible metal-induced formation of free radical species such as the hydroxyl radical (HO*) during the use of permanent hair coloring products has been demonstrated. These highly reactive species are formed from the reaction of hydrogen peroxide with redox metals such as copper, which are thought to be absorbed by the hair from the from-the-tap wash water. Formation of such radical species has been shown to lead to measurable keratin fiber damage. The incorporation of chelants such as N,N'-ethylenediamine disuccinic acid (EDDS) has been demonstrated to prevent this metal-induced radical formation and thus significantly reduce the fiber damage. This chelant is highly effective due to its ability to specifically bind low levels of copper in the presence of relatively high levels of calcium, as is found in hair.