Hyaluronic Acid
Hyaluronic acid (HA) is one of the most important humectant ingredients in Korean skincare. It is a glycosaminoglycan — a type of large, complex sugar molecule — found naturally in the skin, joints and connective tissue. A single molecule of HA can hold up to 1,000 times its weight in water, making it exceptionally effective for hydration.
Despite the word "acid" in its name, hyaluronic acid is not an exfoliant. It is gentle, non-irritating and suitable for every skin type.
General Information Only. This page provides educational skincare information and is not medical advice. If you have persistent acne, eczema, rosacea, allergies, skin irritation, pigmentation changes or any medical skin condition, please consult a qualified dermatologist or healthcare professional before changing your skincare routine. Individual results vary. Always patch test new products.
How hyaluronic acid works
As a humectant, hyaluronic acid works by attracting water molecules and binding them to the skin. It does not add oil or create a physical seal — it draws water in and keeps it in the upper layers of the skin, resulting in a plumper, smoother appearance and a more comfortable feel.
The key nuance is that HA draws water from its surroundings. In a humid environment, this works very effectively — it pulls moisture from the air into the skin. In a very dry environment, it may draw water upwards from the deeper skin layers instead. This is why sealing HA with a moisturiser or occlusive ingredient is important: it traps the water that HA has attracted and prevents it from evaporating.
Molecular weight — why it matters
HA molecules come in different sizes, and size affects where and how they work:
High molecular weight HA
Sits on the surface of the skin. Creates a film that holds moisture at the surface, giving an immediate plumping and smoothing effect. Less likely to penetrate.
Medium molecular weight HA
Works in the upper layers of the epidermis. Provides a balance of surface hydration and some deeper penetration.
Low molecular weight HA (including sodium hyaluronate)
Smaller molecules that can penetrate into the upper layers of the skin more readily. May deliver hydration at a slightly deeper level, though still within the epidermis.
Many premium Korean skincare products use multiple molecular weights of HA together — targeting both surface and deeper hydration simultaneously. Look for ingredient lists that include both hyaluronic acid and sodium hyaluronate, or products that specifically mention multi-weight HA.
How to apply hyaluronic acid correctly
- 1.Cleanse and follow with a hydrating toner or essence
Leave skin slightly damp — do not pat completely dry
- 2.Apply your hyaluronic acid serum
Press gently into damp skin; do not rub. A small amount goes a long way.
- 3.Follow immediately with a moisturiser
This seals in the hydration that HA has attracted. Do not skip this step, particularly if your environment is dry.
- 4.Apply SPF in the morning
HA does not cause sun sensitivity, but daily SPF is important regardless
Who hyaluronic acid is for
Hyaluronic acid suits all skin types. It is one of the few active ingredients that is genuinely universal:
Dry skin: Deep surface hydration; use under a rich moisturiser
Oily skin: Lightweight hydration without greasiness; gel serums work well
Combination skin: Addresses dryness in cheeks without adding oiliness to T-zone
Sensitive skin: Non-irritating, gentle; one of the safest humectants available
Mature skin: Plumps the appearance of dehydration lines; works well with peptides
Dehydrated skin: Core ingredient for rehydration alongside barrier repair
Frequently Asked Questions
Research references
- Papakonstantinou E et al. Hyaluronic acid: A key molecule in skin aging. Dermatoendocrinol. 2012;4(3):253–258.
- Pavicic T et al. Efficacy of cream-based novel formulations of hyaluronic acid of different molecular weights. J Drugs Dermatol. 2011.