Hyaluronic Acid
Understanding molecular weights, application strategies, and how to use HA correctly.
What is Hyaluronic Acid?
Hyaluronic acid (HA) is a humectant naturally present in skin that holds up to 1000 times its weight in water. Topical HA attracts and binds water from the environment and deeper skin layers to the surface, plumping skin and improving hydration.
HA works differently at different molecular weights—smaller molecules penetrate deeper than larger ones.
Molecular Weight Matters
- High molecular weight (HMW, 1,000+ kDa): Stays on surface; plumps outer layers; best for immediate hydration
- Medium molecular weight (MMW, 50-1,000 kDa): Moderate penetration; balances surface and deeper hydration
- Low molecular weight (LMW, <50 kDa): Penetrates deeper; hydrates lower epidermis
Best approach: Products with mixed molecular weights (all three) provide both surface and deeper hydration. Single-weight products are less effective.
Application Tips
- Damp skin: Apply HA to damp (not soaking wet) skin for better binding of moisture.
- Wait before occlusives: Let HA serum absorb 2-3 minutes before applying moisturizer.
- Layer correctly: Toner/essence → HA serum → light moisturizer → heavier cream (if needed)
- Climate matters: In dry climates, HA can actually dehydrate if humidity is <40%. Ensure moisturizer is layered after.
- Don't overuse: Once daily is sufficient. More isn't better.
Common Mistakes
- Applying to completely dry skin (HA needs moisture to work)
- Using too much product (pea-sized amount is enough)
- Skipping the moisturizer layer after HA
- Expecting dramatic results (HA is a hydrator, not an anti-ager)
- Using only HMW HA (single weights are less effective than blends)
Bottom Line
HA is a hydrating essential for most skin types. Use products with mixed molecular weights, apply to damp skin, and always follow with a moisturizer. It's not a substitute for a proper moisturizer—it works best as part of a layered routine.