1. Oral or nutraceutical cosmetic use of an effective amount of at least one monounsaturated fatty acid, its salt and / or its ester as an active agent for treating and / or preventing imperfections in the color and appearance of the skin, and these imperfections do not constitute a violation, resulting from inflammation, not associated with overproduction of melanin, does not represent a defect in the surface of the skin and does not represent a lack of lightness in color and appearance and skin. 2. The use according to claim 1 for the prevention and / or treatment of blurred skin, dull skin, skin with a heterogeneous color and appearance or skin bearing contamination or dyschromia, and / or to detect radiance of the color and appearance of the skin. The use according to claim 1 or 2, wherein the skin is the skin of the face, neck and / or neckline, and preferably is the skin of the face. The use according to claim 1, wherein said monounsaturated fatty acid, its salt and / or its ester is used in isolated form or in a plant extract. The use according to claim 1, wherein the monounsaturated fatty acid, its salt and / or its ester is used in an oral composition, and wherein the content of said monounsaturated fatty acid, its salt and / or its ester is such that the daily dose varies in the range from 0.5 to 2500 mg / day and, in particular, from 5 to 500 mg / day. 6. The use according to claim 1, wherein said monounsaturated fatty acid is petroselinic acid. The use according to claim 6, wherein said petroselinic acid is used in the form of an oil1. Пероральное или нутрицевтическое косметическое применение эффективного количества по меньшей мере одной мононенасыщенной жирной кислоты, ее соли и/или ее сложного эфира в качестве активного агента для лечения и/или предупреждения недостатков цвета и внешнего вида кожи, причем указанные недостатки не представляют собой нарушение, возникающее в результате воспалительных явлений, не связаны со сверхпродукцией меланина, не пре
