Cosmetic Products and Cutaneous Absorption

The cosmetic efficacy: myth or reality?

Abstract

The concept of "skin barrier" has radically evolved with the progress of scientific knowledge, from that of an inert physical structure merely separating internal organs of the body from the "extemal world" to that of a "smart system" able to selectively regulate a bidirectional flux of substances, dynamically interact with the environment and feed to the rest of the organism informations crucial for homeostasis. The structural and functional complex ity of the skin barrier and the multiple interactions among its components are key elements in determining cutaneous absorption of substances: thus, the result of the contact between any product and the skin depends not only on the chemical and physical characteristics of the product itself or the macro- and microenvironmental conditions of the contact, but also on the characteristics of the cutaneous barrier, its integrity and its functionality, in a dynamic and variable equilibrium. Interaction with skin barrier functions is too often underevaluated or not considered in the laws that regulate the commercialization of topical products for human care. In particular, European Union laws that define medicines, medicai devices and cosmetics appear rather confusing and not based on scientific evidence, but essentially on the declarations of producers about the intended use of products. This often leads to uncertainty about the composition of cosmetics and to extreme dishomogeneity of efficacy and safety data, particularly for which concems interactions with the cutaneous barrier (healthy, altered or frankly damaged).  Since no substance is "neutral" for the skin, new laws are desirable, which require manufacturers to fu lly declare the components of their products and perform rigorous and standardized tests to define ali effects of such products on the cutaneous barrier.