What are cosmetics? And what can they be expected to do? To answer these questions we first need to understand the structure and function of the skin. It is perhaps surprising to remember that the skin is an organ. The skin is the visible surface of our bodies, the tangible limit of our physical selves, which we see and touch every day. We associate it with our most intimate sensations and it bears the visible markings of our time alive.
It is also the largest organ in our body. It covers your entire body and has a surface area of about 2 square metres. Its thickness varies from 0.5mm on your eyelids to 4mm or more on the palms of your hands and the soles of your feet. It accounts for around 16 percent of your total body weight.
The skin is a sophisticated, multipurpose organ. Science is still mapping out the complexities of skin physiology, in particular what chemical substances are in the skin, and how they interact. The more that is understood about the chemical and physiological reactions taking place within the skin, the greater the possibilities for treating and preventing skin disease. Understanding the biochemical pathways of the skin also deepens our knowledge of the ageing process.
Before the mid 20th century the skin was considered to be almost impermeable, and because of this it was believed that cosmetic products had a very limited action on skin function. It is now understood that this was wrong. In recent years there have been significant developments in the relationship between skin structure, skin chemistry, and cosmetic ingredients. There is no longer doubt about the capacity of a large number of ingredients to penetrate the skin and actively benefit skin function.
This brief introduction will be followed by a short articles outlining basic skin function, and 2 articles outlining skin structure. Later articles will introduce some of the skin’s chemical components and explain some of the terminology used by cosmetic chemists. In order to assess the benefits or potential problems of what we put on our skin, it is essential to have an understanding of how the skin works, how and why a product may or may not penetrate it, and what effect individual skin types and conditions may have upon that interaction.