Hyaluronic acid, also know as hyaluronan or hyaluronate, is one of the most widely used active ingredients in cosmetic formulations. 

In wound regeneration, Hyaluronic acid has mainly cosmetic applications. 

Hyaluronic acid is used in cosmetic formulations in concentrations ranging from 0.2 to 1%. 

The maximum concentration of NaHA in a body lotion is 2%. 

Hyaluronic acid and its sodium and potassium salts are important cosmetic ingredients that are incorporated in moisturizing and anti-ageing products. 

Additionally, products that contain HA represent only 5%, while more than 95% of the total products contain sodium hyaluronate. 

Hyaluronic acid and its derivates are incorporated in a multitude of cosmetic products for eye contour, lips, facial, and neck care, anti-cellulite body care, or cosmetic color conditioning in different cosmetic categories: creams, lotions, serums, masks 

Hyaluronic Acid, Sodium Hyaluronate and Potassium Hyaluronate enhance the appearance of dry or damaged skin by reducing flaking and restoring suppleness. 

Hyaluronic Acid is also used to thicken the aqueous (water) portion of cosmetics and personal care products.

When a rate of 1 mg/cm2 of a product is applied, the contribution of hyaluronic acid is 0.02 mg/cm2 of skin.

Hyaluronic acid has many qualities that make it superior to other substances used in skin regeneration, with pronounced moisturizing and anti-ageing effects. 

In skin care formulations, hyaluronic acid can be used as a moisturizing component, because of its hydrophilic nature. 

Using cosmetic products such as creams or lotions that contain Hyaluronic acid helps to moisturize the skin and to improve elasticity, thereby decreasing the depth of wrinkles.

It is assumed that, when applied onto the surface of the skin, hyaluronic acid solutions form an occlusive layer, absorb moisture, thereby hydrating the skin, and default wrinkles filling occurs. 

Hyaluronic acid is assumed to stimulate the migration of epidermal cells. 

Additionally, the occlusive properties given by Hyaluronic acid may allow the biologically active substances incorporated in cosmetics to persist in the skin layers and possibly make it easier for them to penetrate the epidermis. 

According to previous studies, some cosmetic Hyaluronic acid products have been proven efficient in protecting the skin from UV irradiation. 

At the same time, sunscreen products containing hyaluronic acid help to maintain a firmer skin, protecting it from the injurious impact of UV radiation, due to the potential antioxidant effect of Hyaluronic acid.

In cosmetic formulations, hyaluronic acid has the function of a viscosity modifier and/or a skin conditioning agent. 

Hyaluronic acid is mainly used in anti-ageing cosmetic products. 

Low Molecular weight-hyaluronic acid has the ability to enhance the level of moisture of the skin and expedite regeneration. 

High Molecular weight-hyaluronic acid forms a viscoelastic film when applied onto the skin and has a moisturizing effect. 

The main action of the High Molecular weight-hyaluronic acid polymer is film forming and it reduces evaporation of water from the skin and thus possessesan occlusive effect. 

Hyaluronic acid is also of particular importance as a delivery system of active ingredients. 

Currently, there are some commercially available formulations incorporating actives in different concentrations. 

These products are designated for the topical treatment of actinic keratosis and skin inflammatory diseases. 

It has been proven that Hyaluronic acid enhances the penetration of the active ingredient through the stratum corneum (SC), which behaves as a barrier to the entry of the molecule into the deeper layers of the skin, and the holding and locating the active ingredient in the epidermis. 

Topical preparations containing Hyaluronic acid in formulation are used for their healing properties, decreasing the skin irritation. 

A topical preparation that contains Hyaluronic acid (0.2% w/w sodium hyaluronate (NaHA)) as a main component is currently available for the amelioration of acute and chronic wounds (areas of grafted skin, post-surgical incisions, etc.).

A significant number of in vitro and in vivo studies have shown the effectiveness of Hyaluronic acid treatment as: anti-inflammatory, skin regeneration and chondro-protective effect, anti-ageing and immunosuppressive effects, etc.

Hyaluronic acid is a glycosaminoglycan constituted from two disaccharides (N-acetylglucosamine and D-glucuronic acid), isolated initially from the vitreous humour of the eye, and subsequently discovered in different tissues or fluids (especially in the articular cartilage and the synovial fluid). 

Hyaluronic acid is a polysaccharide belonging to the glycosaminoglycans, made up of disaccharide units constituted of N-acetylglucosamine and D-glucuronic acid. 

Hyaluronic acid is a component of the connective, epithelial, and neural tissues and it represents a substantial constituent of the extracellular matrix 

Hyaluronic acid is ubiquitous in vertebrates, including humans, and it is involved in diverse biological processes, such as cell differentiation, embryological development, inflammation, wound healing, etc. 

Hyaluronic acid has many qualities that recommend it over other substances used in skin regeneration, with moisturizing and anti-ageing effects. 

Hyaluronic acid molecular weight influences its penetration into the skin and its biological activity. 

Considering that, nowadays, hyaluronic acid has a wide use and a multitude of applications (in ophthalmology, arthrology, pneumology, rhinology, aesthetic medicine, oncology, nutrition, and cosmetics), the present study describes the main aspects related to its use in cosmetology. 

The biological effect of Hyaluronic acid on the skin level and its potential adverse effects are discussed. 

Hyaluronic acid is a natural substance found in the fluids in the eyes and joints. 

Hyaluronic acid acts as a cushion and lubricant in the joints and other tissues.

Among the many biological effects, Hyaluronic acid is involved in cell differentiation, embryological development, inflammation, wound healing, viscoelasticity, etc.

IUPAC name: (1→4)-(2-Acetamido-2-deoxy-D-gluco)-(1→3)-D-glucuronoglycan

Systematic IUPAC name: Poly{[(2S,3R,4R,5S,6R)-3-acetamido-5-hydroxy-6-(hydroxymethyl)oxane-2,4-diyl]oxy[(2R,3R,4R,5S,6S)-6-carboxy-3,4-dihydroxyoxane-2,5-diyl]oxy}

CAS Number: 9004-61-9 

31799-91-4 (potassium salt) 

9067-32-7 (sodium salt)[ECHA]

EC Number: 232-678-0

EC / List no.: 232-678-0

CAS no.: 9004-61-9

Chemical formula: (C14H21NO11)n

Solubility in water: Soluble (sodium salt)

Different forms of hyaluronic acid are used for cosmetic purposes. 

Hyaluronic acid might also affect the way the body responds to injury and help to decrease swelling.

Hyaluronic acid (abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues.