What is hyaluronic acid and how does it work in skincare and makeup?

Hyaluronic acid (HA), along with its cousin sodium hyaluronate, is an immensely popular ingredient in skincare and makeup. It’s also naturally found in the body. Most of it dwells in the extracellular matrix, the scaffold which holds up the cells of your skin. Hyaluronic acid is found in both the epidermis and the deeper dermis, where it’s important in hydration, metabolic processes, skin repair, and protection against free radical and UV damage.

 

 

Hyaluronic acid is a glycosaminoglycan, a class of chemicals that can hold onto water very efficiently, due to its very polar nature. Hyaluronic acid keeps skin firm and plump this way. It’s been thought that decreased hyaluronic acid levels led to the thinner and drier look of aged skin. However, the research currently suggests that the amount of hyaluronic acid in the skin doesn’t actually decrease with age, but it does redistribute with both natural and environmentally-induced skin aging.

In skincare, hyaluronic acid is mostly used for its incredible ability to hold onto moisture: it’s included in moisturisers and serums as a humectant ingredient. Humectants hydrate the skin, and since one of the effects of dehydrated skin is fine lines and wrinkles, this can make your skin look dramatically younger and less tired. Another popular and cheaper humectant moisturiser is glycerin, but glycerin can feel sticky and heavy. Hyaluronic acid is frequently combined with glycerin to make it feel lighter on the skin.

The hyaluronic acid used in skincare isn’t all the same. It’s usually divided into different sizes: there’s high molecular weight hyaluronic acid, which has a larger molecular size, and low molecular weight hyaluronic acid, which is formed by chopping it into smaller fragments. “Sodium hyaluronate” usually indicates smaller fragments than “hyaluronic acid”, but even within those names there are a range of molecular sizes. The main significance of the different sizes is that smaller molecules are able to penetrate the skin better than larger molecules, which means that low molecular weight hyaluronic acid can hydrate deeper than high molecular weight hyaluronic acid, which holds onto water at the surface of the skin.

There’s some debate on how low molecular weight hyaluronic acid can act as an inflammatory signal and therefore be harmful, but it’s important to remember that inflammation isn’t always a bad thing. Studies on skin and skin cells have found that low molecular weight hyaluronic acid can improve the skin’s ability to repair itself, its defense against microbial attack and help with conditions like seborrheic dermatitis. Hopefully there’ll be more research into its effects on normal skin too.

However, don’t be fooled into thinking that applying hyaluronic acid on your skin can help replenish your natural stores! Unfortunately, even low molecular hyaluronic acid can only penetrate into the lower epidermis. It’s a fantastic hydrating ingredient, and hydration is fantastic for improving how well your skin functions. There’s also a bit of anti-inflammatory and antioxidant activity, but the vast majority of its benefits are to do with hydration.

Hyaluronic acid can also come from different sources. The two main sources are biofermentation (made by bacteria) and… rooster combs, which contain about 15 times as much hyaluronic acid as human skin. Yeah, those dangly things on chickens. If you’re vegetarian, you’ll want to look into the source of the hyaluronic acid in your products.

Apart from skincare, you’ll find dehydrated hyaluronic acid spheres in makeup as well, particularly in skin-smoothing primers. The dry spheres are mixed into a water-free (anhydrous) formula. The product is applied on the skin and sinks into any fine lines and wrinkles. The hyaluronic acid spheres start grabbing onto any water molecules it touches from the skin and the air, and the swelling effect hides lines.

In other areas of skincare, chemically modified hyaluronic acid is also used in injectable fillers like Juvéderm Restylane and Voluma to plump up deep wrinkles. It’s also the basis of Macrolane, a controversial filler that’s been used for breast and buttock enhancement. Oral supplements of hyaluronic acid are sold in nutrition stores but there’s no demonstrated benefits yet (it’s questionable whether hyaluronic acid survives digestion, and can make it from the digestive tract to the skin).

So far, my favourite hyaluronic acid product has to be For Beloved One Hyaluronic Acid GHK-Cu Moisturising Serum (click for full review), which has made my skin unbelievably plump and bouncy. I can also vouch for Indeed Labs Hydraluron (review). I haven’t personally tried Hylamide Low-Molecular HA Rehydration Booster but I’ve heard good things about it. Other budget options with great reviews are Timeless Hyaluronic Acid and Hada Labo Rohto Gokujyn Hyaluronic Acid Lotion.

Corrections

2025-11-25: Removed 1 gram of hyaluronic acid can hold onto 6 litres of water – this is from an Int J Toxicol article authored by members of the Cosmetic Ingredient Review panel. The source they cite has no reference for this claim which is, in hindsight, pretty questionable to begin with.

This is a nice example of how “fun fact” style claims in the introductions of peer-reviewed articles aren’t necessarily reliable, even if the journal and authors are well-respected – myths are rampant throughout science! It’s worth being skeptical especially if the claim is tangential to the authors’ expertise, and especially if they’re not directly relevant to the main topic of the article. This article by Borchers and Pirrung in J Cosmet Sci breaks down this myth in more detail. 

References

S Gariboldi et al., Low molecular weight hyaluronic acid increases the self-defense of skin epithelium by induction of beta-defensin 2 via TLR2 and TLR4 (open access), J Immunol 2008, 181, 2103-2110.

M Essendoubi, C Gobinet, R Reynaud, JF Angiboust, M Manfait & O Piot, Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy, Skin Res Technol 2016, 22, 55-62.

T Schlesinger & C Rowland Powell, Efficacy and safety of a low molecular weight hyaluronic acid topical gel in the treatment of facial seborrheic dermatitis final report (open access), J Clin Aesthet Dermatol 2014, 7, 15-18.