22 | www.CosmeticsandToiletries.com Vol. 130, No. 7 | September 2015
RESEARCH | C&T
Reproduction in English or any other language of
all or part of this article is strictly prohibited.
© 2015 Allured Business Media.
As we all know, skin is a unique barrier comprising, from outside to inside, the epidermis, dermis and hypodermis; and that it includes appendages such as hair follicles, sweat and sebaceous glands. From
a penetration perspective, the epidermis and dermis appear to be the most
The main barrier function of the skin is attributed to the Stratum
Corneum (SC), through which transdermal delivery (TD) of chemicals
takes place. 1, 2 Transdermal delivery of drugs, which is routinely used for
delivery of medications including hormones and analgesics, is an effective
and widely used delivery route for many conditions. It involves the passage
of therapeutic drugs through the skin and into the general circulation for
systematic effects. 3
Topical drug application produces a higher local concentration of the
drug, where it preferentially distributes, persists and achieves sufficient
levels of concentration to exert local therapeutic activity. 4 Percutaneous
penetration is also effective for the distribution of drugs to the surface of the
skin, so it can affect the efficacy of topical formulation. 5
At least 15 factors6 affect percutaneous penetration:
•;Physiochemical properties of the penetrant
•;Dose, duration, surface area and frequency of exposure
•;Regional variation in flux
•;Population variability in absorption
•;Skin surface conditions
•;Skin health and integrity
•;Substantivity and binding to the SC, epidermis and dermis
•;Distribution of chemical to epidermis, dermis and sebaceous glands
•;Loss from skin surface and exfoliation
•;Metabolic and photochemical transformation in absorption into and
Niloufar Mohajerani and Kasra Afzali
University of California, Davis, CA
Howard I. Maibach, M.D.
University of California, San Francisco, CA
Validating the Effectiveness of Rubbing on
percutaneous penetration •
effect • epidermis • dermis •
absorption • rubbing
The effect of rubbing on
has long been questioned.
Existing data regarding
rubbing effects is sparse,
and what is available
is controversial at best.
While some evidence
suggests that rubbing
others note the opposite.
of the rubbing effect on
may offer a more complete
picture in relation to the
application of drugs,
cosmetics and skin care.