It is my first article on the beauty section and sometimes it is good to be back to basics. Even if it is obvious probably for most of you, I would like to get back today on the skin and its surface structure.

Often one can get a great challenge to choose a cream or to understand what cream to apply. Well I would say it is not a question of cream, it is a question of how your skin is made!

The most fantastic and out layer of skin is called the Stratum corneum (SC). It is the very top of epidermis, an important layer of the skin. In the SC one can find four to twenty layers. It takes an average of 14 days for the cells in the inferior SC layer to move up to the surface and then leave our body. Every day we lose millions of skin cells but we cannot feel it… It happens on my skin now as I am writing and it happens on your skin as you are reading :)!

The barrier function of the SC is not absolute; some molecules can go through it! This process is called the passive diffusion, I summarized this mechanism on my below sketch. If you apply on top of your skin a cream with a concentration of active ingredients, it could penetrate into the stratum corneum.

Well it is not so simple as the top layers of the skin are made of lipids and flat cells. Also there is a gradient of water in our skin, in depth it exists plenty of water however as the layers move up the water and the living cells are replaced by lipids and cells full of keratin, the major protein of epidermis… At the very top no water anymore, mainly lipids and flat cells the corneocytes !

What does it mean? It means the polar molecules (molecules which love water) or what one call the hydrosolubles molecules, will not penetrate by themselves. Let’s say you get a toner (alcohol free) it will not penetrate the SC. While it can be a good strategy to clean or gently remove surface hydrosoluble impurities, there is almost no diffusion of toner components into the SC.

To be able to penetrate the SC a cosmetic should mix a certain percentage of oil and water.
The oil of a cosmetic formula can be seen as key to open the doors of the skin. It will help the water and other water soluble components to diffuse into the SC. The precious flower extracts, active ingredients or other fantastic compounds in the cream can play their roles to embellish the skin!

When you decide about your beauty routine, just keep in mind this very simple guidance. No penetration = water formulation (alcohol free) this product will act at the surface.  To deliver great ingredients such as antioxidants or moisturizers use cosmetics with a mix of oil and water (emulsions). Most emulsions contain a ratio of 80/20 water in oil.

Always keep in mind one thing, the skin is alive so be gentle with it 🙂 !

Alexandre R Rio.