How Deep Do Different Weights of Hyaluronic Acid Go?

Not all hyaluronic acid molecules act the same. Their molecular weight (size) determines how deep they can travel into the skin. Here’s a breakdown:

Ultra-High Molecular Weight (UHMW-HA)

• Size: >1,500 kDa

• Where it stays: Mostly on the skin surface.

• Effect: Forms a breathable, invisible film that smooths and prevents water from escaping (occlusive effect). Great for instant softness, but doesn’t go deeper.

High Molecular Weight (HMW-HA)

• Size: ~1,000–1,400 kDa

• Where it stays: Upper stratum corneum (outermost barrier).

• Effect: Strong humectant — pulls in water and makes skin feel plump at the surface.

Medium Molecular Weight (MMW-HA)

• Size: ~100–900 kDa

• Where it goes: Can penetrate further into the stratum corneum layers, but usually not past the barrier’s lipid-rich midsection.

• Effect: Improves elasticity and texture, hydrates a little deeper than HMW.

Low Molecular Weight (LMW-HA)

• Size: ~20–100 kDa

• Where it goes: Reaches the lower stratum corneum and in some cases the top of the stratum granulosum.

• Effect: Hydration closer to living cells, supports suppleness, and may help regulate barrier proteins.

Ultra-Low Molecular Weight (ULMW-HA)

• Size: <10 kDa 

• Where it goes: Can penetrate through the stratum corneum into the stratum granulosum, and in some studies even influence layers just above the basal cells (without entering the dermis).

• Effect: Deeper epidermal hydration + signaling, helping skin maintain flexibility and resilience.

The Takeaway

• Big HA molecules = surface plumping & water lock.

• Small HA molecules = deeper hydration & barrier support.

• The smartest serums combine them all, creating hydration at multiple levels — from the surface film down to the living epidermis.

Do you want me to now illustrate this as a skin-layer infographic (epidermis cross-section with arrows showing how far each HA weight travels), so it pairs visually with this blog text?