Abstract
Cosmetics and their primary ingredients can be categorized according to their purposes. Some of them must be penetrated into the stratum corneum or be absorbed into the viable epidermis and dermis, and the others may just cover the skin surface to obtain their cosmetic effects. In addition, some cosmetics must be concentrated into the hair or hair follicles, not into the general skin surface. Thus, we must pay attention to the adequate properties of skin penetration/permeation of cosmetic ingredients for their purpose as cosmetics. I review skin penetration and permeation properties of cosmetic ingredients, experimental and evaluation methods of the skin permeation of materials, and regulation and enhancement methods for the skin penetration, distribution and permeation of cosmetic ingredients in a question and answer system.
