Disclosed is a lanthionizing composition that comprises a lanthionizing agent, such as guanidine hydroxide or sodium hydroxide, and a reduced malto-oligosaccharide. Also disclosed is a method for lanthionization, the method comprising applying to the hair the lanthionizing composition of the invention.

Compositions, optionally heat-activated, methods, two-step methods, and kits for caring for, treating or durable conditioning of at least one keratinous fiber comprising at least one compound comprising at least two quaternary ammonium groups; and at least one sugar chosen from C.sub.3 to C.sub.5 monosaccharides; and heating the at least one keratinous fiber.

Compositions, optionally heat-activated, methods and kits for protecting keratinous fibers from extrinsic damage or repairing keratinous fibers damaged by extrinsic conditions by applying to keratinous fibers a composition comprising at least one compound comprising at least one C.sub.5 to C.sub.7 saccharide unit substituted with at least one amino group and derivatives thereof, and heating the keratinous fibers.

Compositions, optionally heat-activated, methods and kits for protecting keratinous fibers from extrinsic damage or repairing keratinous fibers damaged by extrinsic conditions by applying to keratinous fibers a composition comprising at least one compound chosen from C.sub.3 to C.sub.5 monosaccharides substituted with at least one C.sub.1 to C.sub.22 carbon chain, and heating the keratinous fibers.

A composition comprising at least one hydroxide compound and at least one complexing agent effective for dissociating the at least one hydroxide compound in sufficient quantity to effect lanthionization of keratin fibers. The at least one complexing agent is chosen from compounds comprising at least one group of formula (I) and salts thereof. Also disclosed is a method for lanthionizing keratin fibers to achieve relaxation of the keratinous fibers and a multicompartment kit comprising an activating composition and at least one hydroxide compound.