Certain ingredients in the outer layer of the skin naturally maintain skin moisture content. These substances are called Natural Moisturizing Factors Agents (NMFs). NMFs contain amino acids, pyrrolidone carboxylic acid (PCA), urea, lactate, and salts. The removal or reduction of NMFs leads to dryness of the skin.
Source: semanticscholar.org
Dry skin is a common condition. It is most common during cold winters and becomes more pronounced with age. Moisturizers are typically used to relieve dry skin. As we have seen earlier, three ingredients in moisturizers are used to prevent the emergence of dry skin symptoms: emollients that soften and smooth the skin, occlusives that provide a barrier that sits on the skin surface, preventing loss of skin moisture, and humectants that bind and hold water.
Hydrated skin is elastic, protecting the skin. Enzymes that help retain skin moisture enable the skin to function normally, preventing flaking. A hydrated skin keeps the skin barrier functioning optimally.
The Natural Moisturizing Factors Agents (NMFs) are composed of the following:
| Chemical Composition of NMF | |
| Components | Percentage |
| Free amino acids | 40.0 |
| Pyrrolidone carboxylic acid | 12.0 |
| Lactates | 12.0 |
| Sugars, inorganic acids, peptides, and other unidentified materials | 8.5 |
| Urea | 7.0 |
| Chloride | 6.0 |
| Sodium | 5.0 |
| Potassium | 4.0 |
| Ammonia: uric acid, glucosamines, creatinine | 1.5 |
| Calcium | 1.5 |
| Magnesium | 1.5 |
| Citrate, formate | 0.5 |
| Phosphate | 0.5 |
Source: Joseph Fowler, 2012
The Natural Moisturizing Factors Agents (NMFs) are packed within the dead outermost skin cells of keratin filaments. They are highly efficient humectants, attracting and binding water from the atmosphere even in low relative humidity conditions of 50 percent.
Hydrated NMF helps maintain skin elasticity, keeping it healthy and supple and preventing it from cracking or flaking from mechanical stress. It also balances the osmotic pressure and prevents excessive water influx and loss.
Routine soap washing, exposure to UV light, bathing, and aging cause NMF levels to drop. Aging also dramatically reduces the skin’s amino acid content. Studies have shown a direct correlation between skin hydration and amino acid content. While the outer skin layer may be biologically dead, it is biochemically active. NMF products are breakdown products of the filaggrin protein found in the lower layers of the skin.
Humidity influences the formation of NMF from filaggrin. In humid environments, such as those artificially created with occlusives, NMF formation occurs almost at the outermost surface. It has been shown that occlusive patches applied to the skin can completely prevent filaggrin degradation. NMF formation is also affected by environmental factors, like exposure to UV radiation or skin decline with age. In these conditions, the skin barrier function also declines.
Replacing or replenishing NMF in the skin through the external application of moisturizers containing NMF is effective in treating dry skin. Skincare product manufacturers began including urea in moisturizing creams as far back as 1943. Lactate was also added as an ingredient.
Lactic acid has been shown to stimulate the synthesis of ceramides in the skin. PCA is also now an active ingredient in skincare products. The application of moisturizers with NMF constituents on dry skin conditions has been clinically tested and noted to be effective. (Schleusener J et al.,2021)
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