To obtain the subject inhibitor capable of inhibiting the activity of sebaceous glands, preventing the occurrence of inflammations in the sebaceous glands and treating common acne without forming a common acne trace by including an extract from a plant of the genus Silybum of the family Compositae.

This cosmetic is obtained by including an extract of a plant of the genus Silybum of the family Compositae, e.g. Silybum marianum called Maria-azami, O-azami or Ohire-azami in an amount of preferably 0.0001-10.0 wt.% expressed in terms of a dried substance. In the above extract, silymarin, silybin, silychristin and silydianin, or the like, as active substances are present alone or as a mixture. The extraction from the whole herb of the plant or an individualized material such as leaf, a stem or a fruit is preferably carried out with an organic solvent having an intermediate polarity such as a lower alcohol, a lower polyhydric alcohol, e.g. propylene glycol or acetone or a mixed liquid thereof as a method for extraction.