Some aspects of the role of skin appendages in percutaneous absorption
P. Grasso

Synopsis

The horny layer of the skin (STRATUM CORNEUM) is the principal barrier against the passage into the blood stream of chemical agents applied topically to the skin. This layer contains a number of perforations which lead into the HAIR FOLLICLES, SEBACEOUS GLANDS and SWEAT glands. Early clinical observations have shown that application of certain substances in areas rich in skin appendages results in a much more rapid ABSORPTION than in areas where skin appendages are sparse suggesting that these afford an additional pathway for absorption.

Penetration of topically applied substances into skin appendages was confirmed visually by the application of coloured material on the skin and its subsequent demonstration in the appendages. Quantitative measurements indicate that skin appendages form the major pathway for absorption for a brief but variable period immediately after PERCUTANEOUS application of the test substance. After this period percutaneous absorption occurs mainly through the stratum corneum but a substantial proportion of the test material passes through the appendages. Active transport does not appear to be involved in absorption via the appendages.

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