What exactly is Hyaluronic Acid?

Updated June 2024

If you've been paying even a little bit of attention to the skincare world in the last several years, chances are you've seen the phrase "hyaluronic acid" all over the place. Besides being the backbone of most new hydrating serums, it's also become a common ingredient in moisturizers, lip treatments, and more. 

What is Hyaluronic Acid?

Hyaluronic acid is a naturally occurring compound found throughout the body, particularly in joints, eyes, and in our skin. As a hydrophilic molecule, it draws in and absorbs water well, making it great for keeping things hydrated and moving.

Read more on the basics of Hyaluronic Acid in the human body at the Celeveland Clinic.

Like many beneficial compounds in our bodies, the presence of hyaluronic acid diminishes over time. For skin, that means a loss of not only hydration, but plumpness too, as the volume of water decreases. This is one big contributor to skin appearing more saggy and loose with age.

What can Hyaluronic Acid do for my skin?

Medically injected Hyaluronic Acid (HA) has been used as a filler for over 20 years as part of the growing medical aesthetics market. It's also been used in skincare products for decades, but has increased in popularity as new, more easily absorbed forms of HA are being developed. 

Here are some quick facts about HA and how it can help your skin look and feel better.

1. Hyaluronic Acid is actually not a true “acid”. In skincare, acid usually means exfoliation, but in this case, it's quite the opposite. Despite carrying the name acid, it's actually a polysaccharide, or type of sugar, meaning the HA in skincare products is safe even for sensitive skin. In fact, the only place you'll encounter a hyaluronic acid with a pH low enough to be considered acidic is at a scientific laboratory, when in its purest form.

2. There are two main types of Hyaluronic Acid compounds: high molecular weight and low molecular weight. It that sounds a little too sciency, stick with me for a minute. Hyaluronic acid is a high weight molecule, meaning it's pretty big: too big to penetrate your skin (more on that and how it can still be helpful later). But there are new, low molecular weight forms of hyaluronic acid like Sodium Hyaluronate, Sodium Acetylated Hyaluronate, or Hydrolyzed Sodium Hyaluronate that are much smaller and better able to be absorbed into your skin. 

A product that calls out hyaluronic acid may include high or low molecular weight versions in its formulations, and many use both. We'll go into detail about the benefits you can expect from the two types in the next section. 

3. Hyaluronic Acid is a “hydrator” not a “moisturizer”. Think of it as a drink of water for your skin. Or, imagine adding water to a shriveled up sponge. Immediately the water plumps and expands the sponge (your skin), but over time the sponge will ultimately dry up if not watered regularly. The “sponge” cannot water itself but relies on continuous watering to keep it moist. Your skin reacts to Hyaluronic Acid similarly.

Daily application of a high molecular weight HA product will make your skin appear immediately smoother and plumper, but will shrink back once you discontinue use of the product. 

Products containing low molecular weight forms of HA have less an immediate effect and more a prolonged one. Because they can be absorbed into the skin, the product has more opportunity to interact with skin and may even stimulate reinvigorated HA production by the skin itself. While the effects of lower weight HA last longer, they will still decline over time with discontinued usage, so it's best to think of HA products as a daily enhancer, similar to makeup.


4. Hyaluronic Acid is a humectant that can hold up to 1000x its weight in water. HA can also attract water from outside sources and draw it into your skin. This is meaningful for a couple different reasons. First, you want to remember to apply your HA product prior to a typical moisturizer because the HA can pull and trap the moisture for other products into the skin.

Second, the hydrophilic HA molecule can attract water from the air (humidity) and draw it into your skin, so you will have better results using it in a humid climate.

In very dry areas where there is little to no moisture in the air, HA can backfire and absorb water from your skin, making it feel dry. But don't panic, there's still a way you can benefit from Hyaluronic acid's hydrating properties, even if you live in the desert; you just have to give it some water to absorb.

You have probably heard people say that moisturizers absorb better on wet skin, and the same principle applies here. If you apply an HA serum to wet skin, it will absorb into your skin, along with the water, to properly plump & hydrate your skin.

Who can benefit from using Hyaluronic products in their skincare routine?

Almost everyone, even people with acneic or sensitive skin, can benefit from including hyaluronic acid as part of their regimen.

Acne prone skin can really benefit from HA products as well since it hydrates the surface of the skin, signaling the body to produce less oil. Treating oily and acneic skin with an HA serum can be a great first step to building confidence in “moisturizing” these skin types.

In conclusion, EVERY skin type can benefit from a Hyaluronic Acid serum. Its gentle, hydrating, and you shouldn't experience any breakouts or side effects from using an HA product.