US Patent 7135045 Composition for dyeing human hair

This invention relates to a hair dyeing composition showing excellent dyeing ability comprising at least one direct acting hair dye and benzylurea and/or benzyl carbamate and/or N-(2-methoxybenzyl) urea. The direct acting hair dyes are preferably selected from anionic, acidic dyestuffs. In addition to benzylurea and/or benzyl carbamate and/or N-(2-methoxybenzyl) urea compositions further comprise organic solvents as penetration enhancers. Compositions according to the invention has a pH in the range from 1 to 5 and preferably comprises polymeric thickening agents, organic and/or inorganic acids and conditioning agents.