Use of at least one compound of the formula I where R 1 and R 2 each, independently of one another, denote aryl, a straight-chain or branched alkyl group having 1 to 30 C atoms, which may be substituted by aryl, or a straight-chain or branched alkenyl group having 2 to 30 C atoms, containing one or more double bonds, which may be substituted by aryl, where either R 1 or R 2 may denote H, where R 1 and R 2 together may also form an unsubstituted or substituted five-membered ring, which may be substituted a) by at least one straight-chain or branched alkyl group having 1 to 30 C atoms and/or b) by at least one aryl group having 6 to 12 C atoms and/or c) by at least one straight-chain or branched alkenyl group having 2 to 30 C atoms containing one or more double bonds, where the alkyl group having 1 to 30 C atoms and/or the alkenyl group having 1 to 30 C atoms may be substituted by aryl and/or the aryl group having 6 to 12 C atoms may be substituted by alkyl, OH, Oalkyl, NH 2, NH-alkyl, N(alkyl) 2, C alkyl, O-C alkyl and/or C -Oalkyl, R 3 denotes H or a straight-chain or branched alkyl group having 1 to 30 C atoms and R 4 denotes H or OR 3, where aryl denotes an aryl group having 6 to 12 C atoms, which may optionally be substituted by alkyl, OH, Oalkyl, NH 2, NH-alkyl, N(alkyl) 2, C alkyl, O-C alkyl or C -Oalkyl, and alkyl denotes a straight-chain or branched alkyl group having 1 to 30 C atoms, and/or salts, tautomers, stereoisomers and/or solvates thereof, including mixtures thereof in all ratios, as self-tanning substance. where R 1 and R 2 each, independently of one another, denote aryl, a straight-chain or branched alkyl group having 1 to 30 C atoms, which may be substituted by aryl, or a straight-chain or branched alkenyl group having 2 to 30 C atoms, containing one or more double bonds, which may be substituted by aryl, where either R 1 or R 2 may denote H, where R 1 and R 2 together may also form an unsubstituted or substituted five-membered ring, which may be substituted a) by at least one straight-chain or branched alkyl group having 1 to 30 C atoms and/or b) by at least one aryl group having 6 to 12 C atoms and/or c) by at least one straight-chain or branched alkenyl group having 2 to 30 C atoms containing one or more double bonds, a) by at least one straight-chain or branched alkyl group having 1 to 30 C atoms and/or b) by at least one aryl group having 6 to 12 C atoms and/or c) by at least one straight-chain or branched alkenyl group having 2 to 30 C atoms containing one or more double bonds, where the alkyl group having 1 to 30 C atoms and/or the alkenyl group having 1 to 30 C atoms may be substituted by aryl and/or the aryl group having 6 to 12 C atoms may be substituted by alkyl, OH, Oalkyl, NH 2, NH-alkyl, N(alkyl) 2, C alkyl, O-C alkyl and/or C -Oalkyl, R 3 denotes H or a straight-chain or branched alkyl group having 1 to 30 C atoms and R 4 denotes H or OR 3, where aryl denotes an aryl group having 6 to 12 C atoms, which may optionally be substituted by alkyl, OH, Oalkyl, NH 2, NH-alkyl, N(alkyl) 2, C alkyl, O-C alkyl or C -Oalkyl, and alkyl denotes a straight-chain or branched alkyl group having 1 to 30 C atoms, and/or salts, tautomers, stereoisomers and/or solvates thereof, including mixtures thereof in all ratios, as self-tanning substance. aryl denotes an aryl group having 6 to 12 C atoms, which may optionally be substituted by alkyl, OH, Oalkyl, NH 2, NH-alkyl, N(alkyl) 2, C alkyl, O-C alkyl or C -Oalkyl, and alkyl denotes a straight-chain or branched alkyl group having 1 to 30 C atoms,