The present invention relates to an oxidizing composition for treatment ofkeratin fibers comprising a combinationof； (a) at least one anionic associative copolymer, (b) at least one anionicnon associative copolymer； (c) at least one peroxideagent； (d) at least one persulfate agent； (e) at least on alkalizing agent；and (f) a carrier medium suitable for hair treatment. The oxidizingcomposition described is suitable for composition used in conventional hairtreatments such as dyeing, bleaching, and permanentwaving or relaxing/straightening of the keratinous fibers, particularly humanhair, requiring an oxidizing composition. Thecomposition has good rheology, maintaining its consistency in use, and reducedswelling behaviour in use. Preferred anionic associativecopolymer is acrylates copolymer and preferred anionic nonassociativecopolymer is acrylates/beheneth - 25 methacrylatecopolymer.
