[Academic Presentation] Recent Advances in Research on the Role of Hyaluronic Acid in Restoring Barrier Function in Sensitive Skin

2.1 Overview of Hyaluronic Acid (HA)

HA, also known as hyaluronic acid, is widely distributed in intercellular spaces, the vitreous humor of the eye, synovial fluid, and other connective tissues, and serves as one of the major matrix components of both the epidermis and dermis. It promotes the proliferation and migration of epidermal keratinocytes, thereby facilitating wound healing. Within the dermis, hyaluronic acid provides space and nutrients for collagen fibers and elastin, together forming a structural scaffold that maintains skin tissue integrity, cohesion, and elasticity; it is an essential extracellular matrix component.

2.2 Biological Effects of Hyaluronic Acid in Dermatology

2.2.1 Hydrating Effects of HA The effects of hyaluronic acid on the skin largely depend on its molecular weight: the higher the molecular weight, the stronger its hydrating performance; the lower the molecular weight, the weaker the hydrating effect. High‑molecular‑weight HA is primarily used for skin hydration; when applied to the skin’s surface, it rapidly forms a breathable, hydrated film that envelops the epidermis, softening the stratum corneum and further enhancing the absorption and utilization of active ingredients by the skin, resulting in smoother, more refined skin.

2.2.2 Anti-Aging Effects of Hyaluronic Acid The primary cause of skin aging is the generation of superoxide free radicals upon exposure to ultraviolet radiation, whereas hyaluronic acid possesses the ability to scavenge these oxygen‑derived free radicals. Consequently, it can slow down skin aging and protect the skin from damage. When the skin is exposed to sunlight, it may become reddened, painful, or develop peeling; in such cases, cosmetics containing hyaluronic acid can promote the proliferation and differentiation of epidermal cells and, by virtue of hyaluronic acid’s capacity to neutralize oxygen free radicals, help the damaged skin to heal. Sunscreens often incorporate UV absorbers to provide sun protection; however, hyaluronic acid can significantly reduce the penetration of ultraviolet rays and also repair the skin damage caused by the small amounts of UV radiation that do manage to pass through.

2.2.3 Hyaluronic acid (HA) participates in skin wound healing. Skin repair proceeds through three phases: the inflammatory phase, the proliferative phase, and the remodeling phase. During the inflammatory phase, the synthesis of high‑molecular‑weight HA increases; its water‑retaining capacity causes swelling of the tissues surrounding the wound, creating a porous scaffold conducive to cellular migration to the injury site and inhibiting neutrophil infiltration, thereby attenuating the inflammatory response. In the proliferative phase, low‑molecular‑weight HA promotes fibroblast migration into the wounded tissue; these fibroblasts synthesize collagen and glycosaminoglycans (GAGs), thereby establishing a new extracellular matrix (ECM). HA also stimulates angiogenesis and enhances the proliferation and migration of keratinocytes. During the remodeling phase, HA facilitates both normal and pathological scar formation while exerting antibacterial and anti‑inflammatory effects.

3.1 Hyaluronic Acid and the Skin’s Physical Barrier

A compromised skin barrier in sensitive skin leads to reduced moisturizing capacity, manifesting as increased transepidermal water loss (TEWL), resulting in dryness, flaking, and heightened sensitivity. Hyaluronic acid, when bound to proteins, forms larger proteoglycan molecules that create a gel‑like structure of hyaluronic acid–protein–water, serving as a key component for maintaining skin hydration. It helps retain moisture, prevent chapping and the formation of wrinkles, and, when applied topically, exhibits hydrating, lubricating, film‑forming, epithelial‑regenerating, and safety‑enhancing properties. Sun Min et al. treated 98 patients with facial seborrheic dermatitis using hyaluronic acid–containing moisturizing skincare products and found that, after four weeks, the mean severity scores for facial erythema, scaling, papules, and pruritus, as well as measures such as skin hydration and TEWL, were significantly improved, suggesting that topical hyaluronic acid possesses exceptionally strong moisturizing effects.

3.2 Hyaluronic Acid and the Moisturizing Effect of the Skin’s Lipid Barrier

A deficiency of linoleic acid in the skin’s lipid barrier leads to abnormal permeability of the stratum corneum, increasing transepidermal water loss and resulting in dry, flaky skin. At the same time, the skin’s anti-inflammatory capacity is diminished, making it more susceptible to infection. Sensitive skin often arises from the disruption of lipid components such as linoleic acid within the lipid barrier. Hyaluronic acid, with its hydroxyl, carboxyl, and other polar groups, can form hydrogen bonds with water molecules, thereby binding substantial amounts of moisture. Owing to its excellent film-forming properties, hyaluronic acid can create a uniform protective layer on the skin’s surface, reducing water evaporation and providing an optimal moisturizing environment. Clinical observations by Liu Fuhua et al. have confirmed that hyaluronic acid–based reparative biomembranes restore the skin barrier and deliver robust hydration. Furthermore, a mouse model of superficial dermal injury and skin barrier disruption induced by laser treatment, established by Xu Liangheng, demonstrated that hyaluronic acid dressings promote skin barrier repair.

In addition, studies have shown that hyaluronic acid forms a protective film primarily composed of high-molecular-weight sodium hyaluronate, which helps shield the skin from adverse external factors, bacteria, and allergens, maintains a locally moist environment, protects minor wounds, reduces inflammatory responses, promotes the restoration of the skin barrier, and enhances the skin’s tolerance.

3.3 Hyaluronic Acid and Antioxidant Activity in Local Skin

Prolonged exposure of the skin to ultraviolet radiation leads to a marked reduction in linoleic acid in sebum, compromising the epidermal barrier. This disruption triggers the upregulation of proliferative keratins (K6 and K16) and inflammation‑related keratins (K17), thereby eliciting an inflammatory response. These findings underscore that in sensitive skin, barrier dysfunction results from keratin denaturation within the stratum corneum, with loss of normal structural integrity, diminished capacity to protect against UV radiation and other environmental stressors, increased susceptibility to sunburn, and heightened melanin production—conditions that can readily give rise to hyperpigmentation. If left unaddressed, such issues may progress to scarring, persistent pigmentation, and chronic facial sensitivity. Hyaluronic acid, meanwhile, inhibits the synthesis of enzymes involved in free radical generation within cells, thereby reducing free radical formation and playing a critical role in safeguarding cellular structures, preventing lipid peroxidation, and mitigating age‑related decline. Low‑molecular‑weight hyaluronic acid further exhibits anti‑inflammatory properties, suppresses bacterial proliferation, and helps maintain smooth, radiant skin.

3.4 Hyaluronic Acid and Skin Wound Healing

In sensitive skin, perivascular inflammatory cell infiltration is observed in the dermis, accompanied by intracellular and intercellular edema in the epidermis. Clinically, this manifests as erythema, swelling, and even blisters. Hyaluronic acid within the dermis provides space and nutrients for collagen and elastic fibers, serving as an essential extracellular matrix that maintains skin tissue integrity, cohesion, and elasticity. It also exhibits anti-inflammatory effects, modulates collagen synthesis, and promotes wound healing, thereby creating a favorable microenvironment for repairing the skin barrier and facilitating lesion recovery. Neuman et al. demonstrated that applying hyaluronic‑acid‑containing aqueous cosmetics to mildly burned skin can alleviate pain and accelerate healing, further supporting the notion that topical hyaluronic acid can regulate excessive wound contraction and reduce scar formation. In vitro studies by Prosdocimi et al. further revealed that hyaluronic acid effectively mitigates ethanol‑induced apoptosis in skin cells. Moreover, low‑molecular‑weight hyaluronic acid can penetrate the intact skin barrier into the dermis, directly stimulating cellular proliferation, differentiation, and tissue remodeling and repair. It also exerts additional reparative and cosmetic benefits, including suppression of inflammatory responses, promotion of angiogenesis, improvement of intermediary metabolism, enhancement of nutrient absorption, and increased skin elasticity.