Ingredient Deep Dive: What Does Hyaluronic Acid Do?

Hyaluronic acid is a powerful skincare ingredient with a remarkably simple function: to hydrate the skin by binding and retaining water.

Along with other key components of the skin, like natural moisturizing factors, Hyaluronic acid works to support skin’s moisture for a plump, healthy-looking complexion.

Hyaluronic acid is featured in many of The Ordinary’s formulations and makes an excellent addition to any skincare regimen. In this ingredient deep dive, we break down the basics, the effects of hyaluronic acid, and its long-lasting benefits for your skin.

July 30, 2026

What is Hyaluronic Acid?

Hyaluronic acid is a hyaluronan, a naturally occurring substance throughout the body, found in the skin, eyes, joints, connective tissues, and muscles. Hyaluronic acid is a powerful humectant, a substance that attracts and holds onto water. It helps maintain skin’s moisture, acts as a lubricant.

Because it’s found abundantly in the body, hyaluronic acid supplements, topical hyaluronic acid, and injectable forms, like hyaluronic acid fillers, are generally considered safe. This versatile ingredient is commonly added to skincare serums and moisturizers for hydration, plumping, and age-related concerns.


What Does Hyaluronic Acid Do For Skin?

The molecular structure of hyaluronic acid has multiple points that can hold onto water molecules. When applied to the skin, hyaluronic acid will do just that: hold onto water to help keep the skin hydrated.

For this reason, hyaluronic acid is frequently referred to as a water magnet. Its attraction to water molecules helps the skin retain water. There’s a common misconception that hyaluronic acid causes dehydration by drawing water from deeper layers of the skin, especially in dry environments. However, there is a lack of strong evidence that shows this to be true. Hyaluronic acid’s bonds with water aren’t so strong that they can attract or pull in moisture from elsewhere.


Hyaluronic Acid Benefits for Skin

Hyaluronic acid has several benefits for skin related to water retention. Using a hyaluronic acid serum in your skincare routine can support:

  • Immediate hydration and plumping: Hyaluronic acid draws moisture to the skin’s surface, providing an instant boost in hydration that visibly plumps and refreshes the skin.
  • Reduction in the appearance of fine, dry lines: By keeping skin hydrated, hyaluronic acid helps to reduce the look of fine lines that are often more noticeable when the skin is dry or dehydrated.
  • Enhanced skin smoothness and softness: The added hydration from hyaluronic acid helps create a smoother skin surface, enhancing softness and improving overall skin feel.
  • Improved skin texture: Proper hydration supports the natural shedding of dead skin, a process that relies on water to keep skin texture smooth.


Is Hyaluronic Acid an acid?

Despite its name, hyaluronic acid isn’t the type of ‘acid’ we often think about when we hear the word, and it doesn’t act like an exfoliator. It gets the “acid” part of its name from its molecular structure. When we talk about hyaluronic acid in skincare, we are usually referring to sodium hyaluronate, the salt form of the molecule.

Hyaluronic acid is a polysaccharide. These compounds can organize themselves into different-sized ‘chains’, ranging from super-small, hydrolyzed hyaluronic acid to a large hyaluronic acid crosspolymer of varying weights.

Picture them like building blocks, attaching and growing to different sizes. It’s this adaptable nature that allows hyaluronic acid to play multiple roles in the body. We find it in many skeletal tissues and organs but most abundantly in the skin, accounting for around 50% of the body’s hyaluronic acid.

Hyaluronic Acid and Aging

Like collagen, our hyaluronic acid levels naturally decline as we get older. The decrease in natural hyaluronic acid levels may contribute to signs of aging associated with water loss, such as fine lines and a decrease in skin elasticity.

Topical hyaluronic acid products can help target these age-related skin concerns. Our bestselling Hyaluronic Acid 2% + B5 (Original Formulation) contains 4 forms of hyaluronic acid that target these concerns. This serum works to hydrate, plump, and smooth the appearance of fine, dry lines.


Hyaluronic Acid Molecular Weights + Penetration

Due to its structure, hyaluronic acid comes in many different molecular weights. Formulations that include multiple weights of hyaluronic acid can penetrate and hydrate multiple layers of the skin’s surface.

This is why our Hyaluronic Acid 2% + B5 (with Ceramides) contains five forms of hyaluronic acid:

  • Low, medium, and high molecular weights: A combination of molecular weights of sodium hyaluronate that provide hydration across multiple levels of the skin’s surface
  • Sodium hyaluronate crosspolymer: A type of hyaluronic acid that forms a protective mesh on the skin's surface
  • Hydrolyzed hyaluronic acid: A very low-molecular weight of hyaluronic acid that supports immediate lasting hydration.



How to Maximize Hyaluronic Acid Benefits

  1. When unsure, patch test
    Before use, apply a small amount to the upper forearm, keep the area dry, and observe for 24 hours. If irritation occurs, rinse immediately and avoid use on the face.

    
    
  2. Less is more
    Apply a few drops to clean, dry skin in the morning and evening. Using too much may leave a residue. Our in-house clinical research team found that damp skin doesn’t necessarily improve hydration.

    
    
  3. Pat in and let dry
    After applying, lightly pat the product in and allow it to dry naturally. Avoid excessive rubbing, as it may cause stickiness.

    
    
  4. Use as directed
    Apply only to unbroken skin and follow instructions. If irritation occurs during use, rinse thoroughly, stop use, and consult a physician.


How Often Should You Use Hyaluronic Acid?

Hyaluronic acid is a gentle, versatile ingredient that fits easily into your daily skincare routine.

  • Perfect for daily skin hydration maintenance: Using hyaluronic acid daily helps moisturise your skin, softening fine, dry lines and supporting your skin barrier.
  • Great for year-round use: Whether it’s winter dryness or summer heat, hyaluronic acid is ideal when you’re looking for consistent hydration.
  • Compatible with most skincare regimens: Thanks to its gentle nature, hyaluronic acid pairs well with other ingredients, making it easy to fit into any skincare routine.
  • Suitable for all skin types: Both our Hyaluronic Acid 2% + B5 (Original Formulation) and Hyaluronic Acid 2% + B5 (with Ceramides) serums offer lightweight hydration for all skin types, without clogging pores.

Our hyaluronic acid serums are designed to deliver lasting hydration for your skin. With regular use, hyaluronic acid can help target loss of elasticity, reduce the appearance of fine, dry lines, and support a plumper, healthy-looking, complexion.