A stable hair straightening conditioner which softens and conditions hair when used as a rinse conditioner and which straightens hair when left in the hair using a one-step treatment process, consisting essentially of effective amounts of a nonionic water-soluble cellulose polymer, polyvinyl pyrrolidone, a di-C.sub.10 -C.sub.22 alkyl di-C.sub.1 -C.sub.3 alkyl quaternary ammonium compound, a C.sub.8 -C.sub.18 alkylamido C.sub.2 -C.sub.3 alkyl di C.sub.1 -C.sub.2 alkyl amine, propylene glycol, mineral oil, a C.sub.8 -C.sub.18 alkanol and cyclomethicone in an aqueous vehicle. Also within the scope of the invention is the process of straightening the hair which comprises the steps of applying the straightener-conditioner composition to wet or dry hair in an amount sufficient to wet the hair, combing the hair to distribute the composition and continuing said combing in the presence or absence of added heat until the hair is substantially dry.

A process for relaxing hair in which the hair fibers undergo minimal swelling is provided, using a composition that decreases the swelling of hair fibers. Use of the composition or process decreases hair fiber swelling during the relaxing process, thereby decreasing structural damage to the hair while increasing hair fiber strength.

A stable hair rinse conditioning composition to provide superior dry feel and high luster properties, comprising about 0.5-15% by weight of a polyvinyl pyrrolidone/vinyl acetate copolymer, about 0.1-10% by weight of at least one hydrophilic cationic quaternary ammonium compound, and a water-soluble nonionic cellulose polymer such as hydroxyethyl cellulose, hydroxymethylpropyl cellulose, etc., in an aqueous vehicle.

An oxidation dye composition for keratin fibers, in particular for human keratin fibers such as the hair, comprising, in a medium which is suitable for dyeing, at least one oxidation dye precursor and optionally one or more couplers, which is characterized in that it also contains an anionic amphiphilic polymer containing at least one hydrophilic unit of an unsaturated olefinic carboxylic acid, and at least one hydrophobic unit which is a (C.sub.10 -C.sub.30)alkyl ester of unsaturated carboxylic acid, preferably exclusively of said (C.sub.10 -C.sub.30)alkyl ester of unsaturated carboxylic acid. The oxidation dye compositions are used in dyeing processes and dyeing devices.

An oxidation dye composition for keratin fibres and in particular for human keratin fibres such as the hair, comprising, in water, at least one oxidation dye precursor and optionally one or more couplers, characterized in that it also comprises a nonionic amphiphilic polymer containing at least one fatty chain and at least one hydrophilic unit, and, therefore the invention also relates to the processes and dyeing devices using the oxidation dye composition.