Hyaluronic acid is a naturally occurring substance in your body that holds moisture, cushions joints, and keeps skin firm. It can bind up to 1,000 times its own volume in water, which is why it shows up in everything from skincare serums to joint injections to eye drops. Your body produces it on its own, but production declines with age, which is part of why skin loses plumpness and joints get stiffer over time.
What It Does in Your Body
Hyaluronic acid is a major component of the extracellular matrix, the scaffolding between your cells that gives tissues their structure. In skin, it fills the spaces between collagen and elastin fibers, maintaining hydration, elasticity, and firmness. It also forms network-like connections with surrounding proteins, giving skin its cushioning properties.
Beyond skin, hyaluronic acid is found in synovial fluid (the liquid inside your joints), the vitreous body of your eye, blood vessel walls, the umbilical cord, and internal organs like the kidneys and lungs. In joints, it acts as both a lubricant and a shock absorber. When you put weight on a joint, the pressure squeezes water out of the hyaluronic acid layer and into the cartilage. This concentrates the remaining hyaluronic acid into a protective gel film, just micrometers thick, that shields the cartilage surfaces from friction damage.
It also plays a role in wound healing. When tissue is injured, hyaluronic acid production ramps up quickly. In the early stages, it helps trigger clotting by binding to fibrinogen, then creates swelling that lets immune cells migrate to the wound site. Later, it draws repair cells in, fills gaps in the rebuilding tissue structure, and promotes the growth of new blood vessels. It even helps regulate inflammation, both ramping it up when needed and dialing it back once the initial immune response has done its job.
How It Works in Skincare Products
Hyaluronic acid in serums and moisturizers works primarily as a humectant, pulling water from the environment and deeper skin layers to hydrate the surface. The molecular weight of the hyaluronic acid in a product determines what it actually does. Higher molecular weight versions sit on the skin’s surface, where they reduce wrinkle depth and improve elasticity and dermal density. Lower molecular weight versions penetrate more efficiently into deeper layers of the skin.
Crosslinked forms of hyaluronic acid, which are chemically modified to last longer, have shown the most significant benefits in research. They outperformed both high and low molecular weight versions at reducing water loss through the skin, retaining moisture within the outer skin layer, and improving overall skin barrier function. If you see “crosslinked” or “cross-polymer” on an ingredient list, that’s what it refers to.
Oral Supplements
Hyaluronic acid supplements, typically sold as sodium hyaluronate capsules, have shown measurable effects on skin in clinical trials. A randomized, double-blind, placebo-controlled trial of 150 healthy adults found that three months of daily oral hyaluronic acid significantly improved skin hydration and elasticity compared to placebo. It also reduced water loss through the skin, lowered sebum levels, and decreased the depth of wrinkles around the eyes.
These results suggest that orally consumed hyaluronic acid does reach the skin in a usable form, though the improvements take weeks to appear and require consistent daily use.
Cosmetic Fillers
Hyaluronic acid is the most widely used injectable dermal filler. Doctors inject a gel form beneath the skin to add volume to areas like the lips, cheeks, and nasolabial folds. Results typically last 3 to 12 months as your body gradually breaks down the filler. However, imaging studies have found that residual filler can persist longer than that initial window, and the injection process itself may stimulate local collagen production for longer-lasting structural effects.
One advantage of hyaluronic acid fillers over other types is reversibility. If the results are unsatisfactory or complications arise, a provider can inject an enzyme called hyaluronidase that dissolves the filler.
Joint Injections
Injecting hyaluronic acid directly into a joint, a procedure called viscosupplementation, is an FDA-recognized treatment for osteoarthritis. The goal is to restore the viscosity of synovial fluid that has thinned with age or disease. Most of the clinical evidence covers knee osteoarthritis, but the approach has also been studied in hips, ankles, hands, shoulders, and the jaw joint. The injections are typically given in a series over several weeks, and some people experience pain relief for months afterward.
Eye Drops for Dry Eye
Hyaluronic acid is an active ingredient in many artificial tear products, typically at concentrations between 0.1% and 0.4%. At the eye’s surface, it lubricates, reduces inflammation, and protects against oxidative damage. In a review of clinical studies, 47 out of 53 treatment groups showed statistically significant improvement in subjective dry eye symptoms compared to baseline. Objective measures like tear film stability and surface damage scores also improved in the majority of cases.
Concentrations between 0.1% and 0.2% appear to offer the best balance of symptom relief and comfort without blurring vision, which can happen at higher concentrations.
Other Medical Uses
The FDA has reviewed hyaluronic acid across a surprisingly broad range of medical devices. Beyond the uses already mentioned, it is used in adhesion barriers that prevent internal tissues from sticking together after surgery, as a bulking agent for urinary or fecal incontinence, as a protective coating for esophageal and gastric lesions, in nasal packing after sinus surgery, and even as an organ spacer during prostate cancer radiation therapy to protect surrounding tissue. Eye surgeons also use a viscoelastic hyaluronic acid solution during procedures to maintain the shape of the eye and protect delicate internal structures.
Side Effects and Safety
Topical hyaluronic acid is well tolerated. Skin reactions are rare, and it is considered safe for most skin types, including sensitive skin. Oral supplements have a similarly mild safety profile in short-term use, though people with a history of cancer should use caution with long-term oral supplementation, as hyaluronic acid plays a role in cell growth and proliferation that could theoretically interact with tumor biology.
For injectable forms, the most common side effects are localized: redness, swelling, tenderness, or bruising at the injection site. These typically resolve within a few days. Rarer complications from dermal fillers include infection and, in uncommon cases, delayed inflammatory reactions that can emerge months or even years after injection, particularly if residual filler acts as a reservoir for bacteria.