Composition for dyeing keratinic fibers comprises a cyclic alpha-dialdehyde (I) and a thiol (II) or disulfide (III). Composition for dyeing keratinic fibers comprises a cyclic alpha-dialdehyde of formula (I) and a thiol of formula (II) or a disulfide of formula (III). A = a 6-50 mono- or polycarbocyclic group or a 5- to 30-membered mono- or polyheterocyclic group containing one or more heteroatoms (N, S, O and/or P), both optionally substituted with halo, 1-4C alkyl, OH, 1-4C alkoxy, CHO, 2-5C alkanoyl, 1-4C alkylthio, 1-4C alkylcarboxy, NO2, sulfonato, ammonio, tri(1-4C alkyl)ammonio, imidazolio, pyridinio and benzothiazolio; R, R' = 1-100C aliphatic groups with 0-30 unsaturations, optionally containing heteroatoms (N, S, O and/or P) and optionally substituted as for A. Independent claims are also included for: (1) dyeing keratinic fibers by applying a composition comprising (I) and a composition comprising (II) or (III); (2) kit comprising a composition comprising (I) in one compartment and a composition comprising (II) or (III) in another compartment.
Composition to dye keratinic fibres comprising at least one ortho- or alpha-dialdehyde and at least one sulphurous compound