Here, we will deep dive through the ins and outs of what hyaluronic acid is, why it is a popular skincare ingredient, and what to look for in skin products that feature this ingredient.
This is our science-heavy version for the nerds. If you want to just learn the basics about this effective ingredient, please click here. Let's go!
What is Hyaluronic Acid?
Hyaluronic acid (HA) is a polysaccharide — meaning it is made up of sugar molecules bonded together. Specifically, hyaluronic acid is formed by repeating units of 2 sugars: d-Glucuronic acid and d-N-acetylglucosamine.
These sugars form chains that can get very large — in fact, several thousands of sugars long. What makes this particular polysaccharide special is that it can make long and loose chains when mixed with water. These long chains can intertwine together forming a jelly that allows hyaluronic acid to hold 1,000 times its weight in water.
This water-attracting and water-holding property makes HA an exceptionally effective humectant. Humectants are usually incorporated into moisturizing serums and creams because they can hold onto water to help hydrate the skin.
Though it consists of simple chains of repeating units of 2 sugars, hyaluronic acid can have a vast number of configurations and forms dependent on its size, salt concentration, pH and associated cations, making it a versatile humectant (Necas et al 2008, Snetkov et al. 2020).
Due to its water holding capacity and versatility, hyaluronic acid holds a unique place in nature, found naturally in many organisms including humans. For this reason, hyaluronic acid has been described as "Nature's Moisturizer" (Necas et al 2008).
It is found throughout the human body including the umbilical cord, synovial fluid, the vitreous of the eye, and in your skin. It is also present in all tissues of the body including skeletal tissues, heart valves, the lungs, and more. Your skin accounts for 50% of your body's total hyaluronic acid content (Papakonstantinou et al. 2012).
The top waterproofing and barrier-forming layers prevent the evaporation of water, while the lower layers of the epidermis and dermis are full of hyaluronic acid to hold that water. Only the dermal layer has blood vessels — the epidermal layers get hydration from diffusion of water from the dermal layer. Hyaluronic acid absorbs water from the bloodstream to maintain hydration.
Loss of either hyaluronic acid or the lipid waterproofing — both of which decline with aging — leads to dry skin.
The dermal layer also contains collagen, elastin, and other structural proteins that form the main scaffolding of your skin. Hyaluronic acid is actually just one of the glycosaminoglycans (GAGs) found in the dermal layer. GAGs is a descriptor for these kinds of polysaccharides that form long linear chains that can hold water. Other GAGs include dermatan sulfate, with chondroitin 4-sulfate and chondroitin-6 sulfate found in smaller amounts.
Together, these structural proteins and water-holding GAGs form the extracellular matrix (ECM) that gives your skin its structure — including its firmness, smoothness, elasticity, and plumpness. GAGs are necessary to maintain skin hydration and turgor, and also play a role in the transport of water-soluble nutritional material to your skin cells. Hyaluronic acid is the most predominant component of the ECM (Papakonstantinou et al. 2012).
Why is Hyaluronic Acid Popular for Aging Skin and Skin Conditions?
Hyaluronic acid is popular as a powerful humectant that is well-tolerated even by the most sensitive skin types — because it is naturally found in the body. Even if you have very sensitive skin or skin prone to allergic reactions like in conditions such as rosacea, eczema, or psoriasis, hyaluronic acid will not cause a skin reaction because it is natural to the skin and will not create an inflammatory, allergic response. In other words, it is universally well tolerated.
As you age, dry skin becomes more and more of an issue. This is in part because natural levels of GAGs like hyaluronic acid decline, contributing to dry skin. With aging, HA disappears from the lower levels of the epidermis, and the size and levels of hyaluronic acid in the dermis decrease as well.
With photoaging, this decline accelerates. Photoaging results in abnormal GAG content with diminished hyaluronic acid and increased chondroitin sulfate proteoglycans. Existing hyaluronic acid is also degraded in photoaged skin (Papakonstantinou et al. 2012). Your skin's water-holding ability decreases the more it is exposed to the sun.
Compounding this is the loss of waterproofing lipids such as ceramides in the top layers of the skin, which allows more water to evaporate, leading to skin dryness.
One solution to this problem is hydrating serums, lotions, and creams applied topically. Humectants like hyaluronic acid love water and hold it, while lipids such as ceramides, oils, waxes, and fats help prevent evaporation of water.
Using a topical product which contains hyaluronic acid basically creates hydration atop of your skin and creates a humid microenvironment which increases moisture content within the skin and limits evaporation of water from the skin.
Hyaluronic acid is so water-loving and so effective a humectant that a little goes a long way. Plus it has no real toxic effects since it is a natural part of your body.
Products made from hyaluronic acid have many other uses outside of skin moisturizers, including artificial tears, wound healing hydrogels, and osteoarthritis treatment (Gupta et al 2019, Snetkov et al. 2020, Li et al. 2020). Hyaluronic acid is naturally involved in wound healing in the human body as well (Chen and Abatangelo 1999).
How to Use Hyaluronic Acid Skincare Products
Hyaluronic acid plays well with other ingredients whether it is found in a serum or a cream. If found in a serum, you can layer it on with other serums, applying serums from thinnest to thickest. If found in a cream, apply that after your serums.
If you are in a very dry environment — such as an arid climate, in winter, or on an airplane — spritz your skin with water first before applying the hyaluronic acid product. Hyaluronic acid is so effective at pulling and holding water that you want it to pull moisture from its environment rather than from your skin.
If you start using your serums and creams soon after you buy them, you can keep them at room temperature. However, if you will not use a product for a while, keep serums and creams with hyaluronic acid in the refrigerator.
This is because at room temperature, hyaluronic acid can slowly degrade over time, which decreases its humectant ability. Refrigeration inhibits the degradation process (Snetkov et al. 2020).
You will also find hyaluronic acid featured in a number of our other products, including:
Why Are There So Many Types of Hyaluronic Acid Available?
The different types of hyaluronic acid represent different lengths (sizes) of the molecule. In its natural state, hyaluronic acid is a very long molecule — several thousands of sugars long. Typically, the hyaluronic acid in your products is shorter. However, for the most part, hyaluronic acid is still too large to enter into your skin as a big molecule. It sits on top of the skin and does not get absorbed.
Over the years, some researchers have made very small sized hyaluronic acid that can penetrate into the skin and lead to improvements in skin hydration and firmness (Essendoubi et al. 2016, Shigefuji and Tokudome 2020, Lubart et al. 2019, Jegasothy et al. 2023, Liu and Nassim 2020).
This strategy is controversial. Small-sized hyaluronic acid that can penetrate the skin may be inflammatory and promote an inflammatory response which can slow down healing (Snetkov et al. 2020, Papakonstantinou et al. 2012, McKee et al. 1996, Lee et al. 2021, Collins et al. 2011, Necas et al 2008). If you want to avoid this, steer clear of anything labeled "hydrolyzed hyaluronic acid" or that otherwise implies the HA has been cut into extra-small pieces to aid penetration.
Decoding the Label: HA by Any Other Name
What may be confusing about hyaluronic acid is that it is also known as hyaluronan — these are names for the same thing. Further, sodium hyaluronate is just the sodium salt version of hyaluronic acid.
That sounds complicated, but think of it this way: table salt is just sodium ions with chloride ions. They are attracted to each other because sodium ions have a positive charge and chloride ions have a negative charge. Hyaluronic acid also has a negative charge so it will attract positive sodium ions. When dissolved in water, the ions separate and you are left with sodium ions and hyaluronic acid.
So overall, applying hyaluronic acid to the surface of your skin should not increase its levels under your skin, since it should not pass the stratum corneum. If you want to increase the levels of hyaluronic acid within your skin, the topical products to use are actually retinoids.
Retinoids can increase hyaluronic acid in the dermis and basal epidermis — and this is part of how retinoids help improve wrinkles (Margelin et al. 1996). If you want to increase hyaluronic acid levels inside the skin, try a retinoid like retinaldehyde, retinol, or tretinoin.
What About Oral Hyaluronic Acid or Hyaluronic Acid Fillers?
Another route by which hyaluronic acid may be increased in the skin is by taking pills orally which contain hyaluronic acid. Research shows that this has benefits for the skin, reducing wrinkles and improving skin suppleness (Oe et al. 2017).
Proceed with caution with oral hyaluronic acid. There is some concern that oral HA formulations may promote the growth of certain cancers. In one study, pancreatic cancer cells were found to "feed" on hyaluronic acid in the surrounding tumor microenvironment (Kim et al. 2021). Oral HA is contraindicated for those with cancer (Simone and Alberto 2015). We suggest consulting your doctor before taking oral hyaluronic acid.
Another option — one that can give you visible results quickly — is to get hyaluronic acid into the dermis with injectable dermal fillers such as Juvederm or Restylane. Injectable fillers can be invasive and damage nerves and blood vessels, however, so go to a reputable medical professional if you take this route.
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