A naturally occurring molecule that can hold up to 1,000 times its weight in water. Used in serums, creams, and masks worldwide, HA is one of the most researched and trusted hydrating ingredients in modern skincare.
A powerful moisture-binding molecule that can hold up to 1,000 times its weight in water, making it exceptionally effective at hydrating and plumping the skin. It works by drawing moisture from the environment and deeper skin layers to the surface, helping to reduce the appearance of fine lines and maintain a smooth, supple complexion. This ingredient is considered very safe for all skin types, including sensitive skin.
Hyaluronic Acid is a linear glycosaminoglycan composed of repeating disaccharides of β4-glucuronic acid-β3-N-acetylglucosamine (CIR, 2023). It is found naturally in the skin, connective tissue, synovial fluid, and eyes. The molecular weight of cosmetic-grade HA ranges from 5 to 1,800 kDa, and 1 gram can hold up to 6 litres of water. For cosmetic use, HA is derived via either bacterial fermentation (using Streptococcus equi subsp. zooepidemicus) or extraction from rooster combs. The CIR Panel noted that bacterially-derived HA is nearly endotoxin-free and preferred over animal sources, which may contain proteins, DNA, and chondroitin sulfate impurities.
According to 2023 FDA VCRP data, Hyaluronic Acid is reported in 663 cosmetic formulations and Sodium Hyaluronate in 4,713 formulations — a significant increase from 601 formulations in 2005. Dermal penetration studies using human dermatomed skin show that MW determines penetration depth: low MW (20–50 kDa) reaches the full epidermal depth of ~100 μm, medium MW (100–300 kDa) penetrates to ~50 μm, while high MW (1–1.4 MDa) is limited to ~25 μm in the stratum corneum. This is why modern multi-weight formulas combine different MW fractions for both surface hydration and deeper delivery.
Draws and retains moisture — 1 g of HA can hold up to 6 litres of water (CIR, 2023). Multi-weight formulas hydrate from the stratum corneum down to ~100 μm epidermal depth.
By filling the skin with water, HA visibly smooths fine lines and wrinkles caused by dehydration, giving skin a more youthful look.
High MW HA (1+ MDa) stays in the stratum corneum at ~25 μm depth, forming a breathable film that reduces trans-epidermal water loss (TEWL) and shields against environmental stressors.
Helps calm irritated skin and supports wound healing. HA plays a natural role in tissue repair and maintaining skin's moisture balance.
Suitable for: All skin types — dry, oily, combination, sensitive, and acne-prone.
The CIR Expert Panel (July 2023) reviewed all available data and concluded that all 7 hyaluronate ingredients — including Hyaluronic Acid — are safe in cosmetics at present practices of use and concentration. EU approved with no restrictions.
In low-humidity environments (<40% RH), low-molecular-weight HA may draw moisture from deeper skin layers rather than the air. Pair with an occlusive moisturizer (ceramides, squalane, or petrolatum) to lock in hydration.
The CIR Panel (2023) stressed that animal-derived HA (rooster combs) may contain infectious agents, proteins, and endotoxins. Look for bacterially-fermented HA, which is nearly endotoxin-free.
This assessment covers topical cosmetic use only. Cross-linked HA dermal fillers have separate INCI names and are not covered by this safety review. The CIR Panel also noted insufficient data to assess safety via airbrush delivery systems.
The CIR 2023 report reviewed multiple developmental and reproductive toxicity studies: subcutaneous injection of HA (up to 60 mg/kg/d) and Sodium Hyaluronate (up to 50 mg/kg/d) in rats and rabbits during gestation showed no fetal abnormalities. Oral teratogenicity studies with Sodium Hyaluronate (up to 1,333 mg/kg bw/d) found no maternal toxicity or teratogenicity. No influence on sperm malformation was observed. Topical HA is generally considered safe during pregnancy, but always consult your healthcare provider.
Start with a gentle cleanser to remove impurities. HA absorbs best on clean, slightly damp skin.
While your face is still damp (or mist with a toner), apply 2–3 drops of HA serum. This gives the molecule water to bind to immediately.
Follow with your moisturizer or cream to create an occlusive seal, trapping the moisture HA has drawn in. In dry climates, this step is essential.
Best for layering. HA used at up to 0.83% in leave-on products (CIR, 2023). Fast absorption, ideal for oily and combination skin.
Hydration + occlusion in one step. Better for dry skin and cold, low-humidity environments.
Intensive 15–20 min treatment. Great for weekly hydration boosts or before special events.
Strengthens the skin barrier while HA hydrates. Complementary mechanisms, no conflict.
HA hydrates and plumps; Vitamin C brightens and fights free radicals. Apply Vitamin C first.
Occlusives that seal in the moisture HA delivers. The ideal HA follow-up, especially in dry climates.
HA counteracts the dryness retinol can cause. The CIR report notes HA can moderate the penetration of other chemicals, making it a good buffer layer before actives.
Very low pH products can temporarily reduce HA efficacy. Wait 5–10 minutes between acid and HA application.
Without an occlusive layer, HA may draw moisture from your skin rather than the air. Always seal with moisturizer.
Found in 2,973 product variants in our database. Here are some well-known options:
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