The skin is the first barrier that protects our organism and our internal balance from external challenges. As such, the skin helps to combat dehydration and prevents the entry of pathogens (viruses, bacteria, allergens, etc.). The skin’s barrier function is vital to protecting the body’s integrity.

To do so, our skin has been designed by evolution with an external layer made up of cornified cells (called corneocytes). These cells are linked together, like bricks in a wall, with an intercellular lipidic cement that confers water-impermeability to the skin.

Additionally, this superficial cutaneous layer is coated with the hydrolipidic film. As the name implies, this protective film is a natural emulsion made up of water and lipids. The aqueous part of this emulsion comes from both dermal water that rises through the epidermis (and which can also be produced through perspiration), and water from the atmosphere that comes to rest on the skin. The lipid component of the emulsion is made up of sebum. Sebum is a kind of fat produced by the sebaceous glands, and helps make the surface of the skin impermeable and naturally acidic.

Together, epidermal intercellular lipids and the hydrolipidic film constitute a natural protective barrier on the skin’s surface that protects us from external aggressions and water loss.