Synergistic combinations of active substance for the cosmetic or dermatological care of the skin, hair & nails

Cosmetic and/or dermatologically active compound combinations comprising

• a) an active amount of biotin and/or biotin esters,
• b) an active amount of one or more .alpha.-hydroxycarboxylic acids of the general formula ##STR12## and/or an active amount of one or more .alpha.-keto-carboxylic acids of the general formula ##STR13## wherein R' and R" independently of one another are chosen from the group consisting of
• (b1) H--,
• (b2) branched or unbranched C.sub.1-25 -alkyl-,
• (b3) branched or unbranched C.sub.1-25 -alkyl- which is substituted by one or more carboxyl groups and/or hydroxyl groups and/or aldehyde groups and/or oxo groups (keto groups),
• (b4) phenyl- and
• (b5) phenyl- which is substituted by one or more carboxyl groups and/or hydroxyl groups and/or branched and/or unbranched C.sub.1-25 -alkyl groups, or wherein the .alpha.-carbon atom of the .alpha.-hydroxycarboxylic acid, together with R' and R", forms a
• (b6) unsubstituted cycloalkyl group having 3 to 7 ring atoms or a
• (b7) cycloalkyl group having 3 to 7 ring atoms which is substituted by one or more carboxyl groups and/or hydroxyl groups and/or oxo groups (keto groups) and/or branched and/or unbranched C.sub.1-25 -alkyl groups,
• and
• where the .alpha.-hydroxycarboxylic acid or the .alpha.-hydroxycarboxylic acids or the .alpha.-keto-carboxylic acid or the .alpha.-keto-carboxylic acids can optionally be present in the form of their physiologically tolerated salts and/or ethyl esters and/or methyl esters,
• and
• c) an active amount of one or more antioxidants.