Hyaluronic acid (HA) is an extremely hydrophilic complex sugar, naturally present in the human body in the joints, muscles, eyes and especially in the skin. Nearly 50% of its total quantity is found in the dermis, the deep layer of the skin. It constitutes the extracellular matrix and serves as a support for collagen and elastin fibers. It also ensures skin hydration because it acts like a molecular sponge: it captures water molecules and retains them.
Epidermal and dermal cells are capable of synthesizing HA. Because the dermis is much thicker than the epidermis, it contains four to nine times more HA. Nevertheless, it has been shown that for the same amount of tissue, the epidermis synthesizes four times more hyaluronic acid than the dermis.
Skin cells lose their ability to produce optimal amounts of HA during the aging process. This is why babies' skin is so soft and smooth: it is rich in hyaluronic acid. However, as we age, dehydration occurs; the skin becomes thinner and wrinkles appear. The decrease in HA production is also accompanied by a decrease in the suppleness, elasticity, and tone of the skin. In mature skin, HA is still present in the dermis, while in the epidermis it has completely disappeared.
Today, the reasons for the precipitous drop in HA with aging are unknown. In order to fight against this phenomenon, it is recommended to continue to “recharge” the skin with HA from adolescence. It is already known that hyaluronic acid ingredient taken orally has no benefits for the skin, as the skin cells are not able to extract it from the bloodstream. The “recharging” of the skin with this compound is more reliable through the topical application of hyaluronic acid skin care products.
But how does HA work on the skin when applied topically?