The cells in the horny layer are bound together by epidermal lipids. These lipids are essential for healthy skin: they create its protective barrier and bind in moisture. When lipids are missing, skin can become dry and may feel tight and rough.

The epidermis is covered by an emulsion of water and lipids (fats) known as the hydrolipid film. This film, maintained by secretions from the sweat and sebaceous glands, helps to keep our skin supple and acts as a further barrier against bacteria and fungi.

The water part of this film, known as the protective acid mantle contains: