Skin Hydration: Everything you need to know about the Natural Moisturising Factor (NMF)

There are elements that ensure hydration and its preservation at the superficial layer of the epidermis. They are also referred to as NMF, the abbreviation of their English name "Natural Moisturising Factors". These are all the hygroscopic substances responsible for maintaining hydration in the stratum corneum of the epidermis, which is the most superficial layer of the skin, directly in contact with the external environment.

The NMF constitutes up to 30% of the total dry weight of the stratum corneum. Approximately one third of the water contained in the stratum corneum is bound to NMF molecules.

In terms of its composition, it contains over 50% of free amino acids and their derivatives such as pyrrolidone carboxylic acid derived from glutamine and the urocanic acid derived from histidine. The amino acids are predominantly derived from the proteolysis of a single protein, the filaggrin. In addition to these, the NMF also includes other species such as lactic acid, urea, ceramides, mineral ions (sodium PCA, potassium, magnesium) and sugars (triglycerides and saccharides). These components are, among other things, derived from the seborrheic secretion by the sebaceous glands.

Furthermore, NMF also contains hyaluronic acid, a complex natural carbohydrate that plays a crucial role in wound healing. It is a potent humectant, capable of binding to over 1000 times its weight in water. It is also the compound that provides structure and elasticity to the skin. Therefore, it is often used for its regenerative properties, particularly in cases of wrinkles or skin sagging.

Atopic dermatitis, psoriasis, ichthyosis vulgaris, and xerosis all result in dry, flaky skin. In patients suffering from these conditions, the levels of Natural Moisturising Factor (NMF) in the stratum corneum are either reduced or absent. Ageing, systematic skin washing with soap, or excessive exposure to UV rays are also known to decrease the levels of NMF in the superficial layers of the stratum corneum.

Therefore, replenishing or restoring the skin's supply of natural moisturising components through the application of moisturising products rich in NMF is a long-standing approach to caring for dry and/or dehydrated skin.

• Marty JP, NMF and Cosmetology of Skin Hydration., Laboratory of Dermopharmacology and Cosmetology, Faculty of Pharmacy, Annals of Dermatology and Venereology, (2002).