Hyaluronic acid benefits: what the trials show

What is hyaluronic acid?

Despite the name, it is not an exfoliating acid. Hyaluronic acid, also sold as sodium hyaluronate or hyaluronan, is a slippery substance found throughout the body, especially in the skin, joints and eyes. Cleveland Clinic says a quarter teaspoon of it holds about one and a half gallons of water, which is why it shows up in so many serums and creams.

In skin, it is not only a deep-layer ingredient. A 2007 review in the Journal of Cosmetic Dermatology notes that hyaluronan is also found in the outer layers, where it helps keep the surface structure and barrier normal.

What has hyaluronic acid been shown to do?

Each row is one published trial. Look at who took part and who paid.

Pavicic 2011, Muhammad 2024, Hsu 2021, Dolečková 2025. Full references under Sources.

Why molecule size matters

Hyaluronic acid comes in chains of very different lengths, measured in kilodaltons (kDa). In the 2011 German trial, every size from 50 to 2,000 kDa hydrated the skin, but only the 50 and 130 kDa versions made wrinkles measurably shallower after 60 days. The authors suggest the smaller molecules get further into the skin. The 2024 Jakarta trial pointed the same way for very dry skin on the legs.

Those are two trials, both small, so treat the size question as promising rather than settled.

What hyaluronic acid does not do

It does not replace a moisturizer. It draws and holds water, but in the Jakarta trial it did not reduce water loss through the skin. That job belongs to the oils and occlusives in a cream. The AAD lists hyaluronic acid next to petrolatum, dimethicone and shea butter in its ingredients for dry skin, and says creams and ointments do more than lotions.

A serum is not a filler. Injected hyaluronic acid fillers are a medical procedure that adds volume. A serum hydrates the surface. Karisma Esthetics does not offer injectables of any kind.

The supplement evidence is young. The two oral trials were positive, ran 12 weeks, and were both run or co-written by employees of the companies that make the ingredient. A 2022 review that also concluded in its favor was written by a paid consultant and employees of L'Oréal.

How to use a hyaluronic acid serum

1. 1Apply to damp skinAfter cleansing, while the face is still slightly wet. The AAD advises moisturizing damp skin.
2. 2Seal it inFollow with a moisturizer or cream within a minute or two, so the water it holds stays in your skin.
3. 3Morning and nightThe 60-day trial used it twice a day.
4. 4Sunscreen on top in the morningBroad-spectrum SPF 30 or higher. Hyaluronic acid offers no sun protection.
5. 5Pair it freelyIt sits well with most actives. Cleveland Clinic notes it may help counteract some of retinol's irritating effects, which is why it often shows up in a first retinol routine.

What about darker skin?

None of the four trials above reports results for Black participants. The Taiwanese study enrolled Asian adults, the Czech one white adults, the Jakarta one Indonesian nursing-home residents, and the German trial's summary does not state ethnicity. So there is no data showing it works differently on melanin-rich skin, in either direction.

Its appeal for darker skin is its gentleness. Cleveland Clinic calls reactions to hyaluronic acid rare. The AAD notes that a product that irritates the skin can cause dark spots, so a hydrating ingredient that rarely stings is a low-risk choice. For dark marks themselves, see vitamin C for dark spots and niacinamide, which have pigment data.