Lactic Acid (INCI name: Lactic Acid): Studies have shown that topical application of lactic acid in small amounts increases skin hydration. Its unique structure gives it the ability to retain water molecules within the epidermis, thus limiting the phenomenon of transepidermal water loss. In addition, another study has shown that it promotes the biosynthesis of lipids in the stratum corneum, in particular ceramides, thus strengthening the skin barrier. Lactic acid would be metabolized into acetyl-coenzyme A, which would then be used as a carbon source for the biosynthesis of lipids;
Aloe vera (INCI name: Aloe Barbadensis Leaf Juice): Due to its composition rich in mono-, polysaccharides and amino acids (histidine, arginine, threonine, serine, glycine, and alanine), studies have revealed that aloe vera extracts help improve skin hydration through a humectant mechanism. In other words, they act by attracting water from other layers of the epidermis to the most superficial layer. As a result, aloe vera has the ability to increase the water content of the stratum corneum, also improving the physical and chemical properties of the skin's surface to make it smooth and soft;
Beta-Glucane (INCI name: Sodium Carboxymethyl Beta-Glucan): Derived from cereals (rice, wheat, barley, oats…) or microorganisms (yeast, bacteria, fungus…), this natural polysaccharide helps slow down the skin's water loss and minimize the appearance of fine dehydration lines. In fact, studies have found that beta-glucan can promote the biosynthesis of skin cells and collagen, despite its large molecular size. It has been shown that beta-glucan can penetrate deep into the skin through the intercellular space;
D-panthenol (INCI name: Panthenol): This compound also has a moisturizing property. Studies have shown that the application of a formula containing panthenol produced a significant decrease in transcutaneous water loss and an increase in the hydration of the stratum corneum, explained by the ability of provitamin B5 to stimulate the synthesis of fatty acids that constitute the protective barrier of the epidermis, thus improving skin hydration;
Lactobionic acid (INCI name: Lactobionic Acid), gluconolactone (INCI name: Gluconolactone), etc.: Thanks to their structure, PHAs are considered to be excellent humectants that have a strong affinity for water molecules due to their numerous hydroxylated groups (-OH). In fact, they have the ability to bind large amounts of water, and retain it in the surface layers of the skin to maintain a plumped up, plumper look;
Glycerin (INCI name: Glycerin): It is one of the most effective humectant polyols alongside sorbitol and mannitol. Glycerol is diffused into the stratum corneum and creates a “reservoir” within the lipid bilayer, where it is thought to interact with the lipid structures or proteins of the stratum corneum to modify their water-binding properties. It is its structure that gives it its moisturizing effects. Glycerin has three hydroxyl groups (-OH) which are responsible for its hygroscopicity. Indeed, they will bind and retain water. However, the moisturizing effect of glycerol on the skin is a function of the quantity absorbed in the stratum corneum: skin hydration increases linearly with the quantity of humectant accumulated;
Niacinamide (INCI name: Niacinamide): Also known as vitamin B3, niacinamide is believed to stimulate the production of ceramides and other intercellular lipids in the epidermis, which in turn help to strengthen the skin's barrier function to limit moisture loss, thus keeping skin hydrated and plumped for longer;
Sodium PCA (INCI name: Sodium PCA): Numerous studies have shown that sodium PCA can increase the water content of the upper layers of the skin. Thanks to their ionic charges, this PCA derivative is able to attract moisture from the air and contain water molecules in the stratum corneum, up to 250 times its weight;
Urea (INCI name: Urea): The moisturizing action of this polar molecule has been widely studied over the years. Data has shown that urea can significantly reduce water loss through evaporation, thus helping to improve and preserve skin moisture levels. Under high humidity conditions, urea is able to increase the water content in the stratum corneum by binding to water molecules.