The skin is the outer covering of the human body and plays an essential role in the preservation of health: it not only defends the body from attacks by viruses and bacteria, but also helps to maintain the balance of fluids and to regulate body temperature.
The skin consists of three superimposed layers, which have different characteristics and functions:
- Epidermis. The outermost layer of the skin protects the body from external agents.
- Dermis. This thick layer of the skin is made up of connective tissue and performs multiple functions: it nourishes the epidermis by removing waste, helps wounds to heal, contains sensory receptors and regulates body temperature.
- Hypodermis. This layer of subcutaneous adipose tissue helps to regulate body heat and provides the body's main energy store.
The skin begins to form in the early weeks of gestation, and in later months becomes covered by a whitish-yellow substance known as the vernix caseosa or "milk crust". This comes away after birth, leaving the skin of the infant vulnerable to harsh external factors. The skin of the newborn infant is more fragile than that of the adult as the hydrolipidic film (the barrier of water and fat that covers the skin) is still very thin and delicate. The hydrolipidic film contains two components:
- A lipid component with protective function.
- An aqueous component with moisturising function (NMF).
The Natural Moisturising Factor (NMF) is a combination of substances with a high capacity to bind and retain the water present on the outer layer of the skin, the stratum corneum, thus regulating its hydration. In the skin of young babies, this natural hydration factor can become depleted for various reasons: including contact with the air, contact with a nappy, or the use of detergents that dry out the skin. This often leads to dehydration, dryness, and greater sensitivity to environmental agents. It is therefore very important to wash and cleanse the skin of newborn infants in the correct way, using products which protect the skin, and which hydrate deeply while keeping the hydrolipidic film intact.