Hydrolyzed Hyaluronic Acid

What it is

This is ordinary hyaluronic acid that has been broken down, usually by enzymes or controlled heat, into much shorter chains. The result is a thinner, less sticky liquid that sinks in quickly instead of sitting on the surface as a tacky film. Brands use it when they want a hydrating serum or essence that feels light, and it is the ingredient behind most "penetrating" or "nano" hyaluronic acid claims. Note that "hydrolyzed" on a label tells you the chains are short but not how short, and there is no standard definition.

What it does well

• Crosses the stratum corneum better than high molecular weight hyaluronic acid

  Ex vivo Raman imaging of human skin found 20-300 kDa hyaluronic acid passing through the stratum corneum while 1000-1400 kDa grades did not. This supports the penetration claim in principle, though the depth reached is measured in micrometres.

  Moderate evidence

• Gives a lighter, less sticky feel at the same hydration level

  Shorter chains build far less viscosity, so a formula can carry more of them without becoming tacky. In a controlled trial in elderly dry skin the low molecular weight version also gave slightly higher measured hydration than the high molecular weight version.

  Moderate evidence

Worth knowing

• Marketing overstates how deep it goes

  "Reaches the dermis", "replenishes your skin's own hyaluronic acid" and "works like a filler" are not supported by topical penetration data. A tape-stripping study could only detect applied hyaluronic acid in the stratum corneum.

  Matters most toAnyone paying more for a product on the strength of deep-penetration claims.

• Very short hyaluronan fragments are pro-inflammatory signals in laboratory models

  In cell and tissue biology, hyaluronan fragment size determines the signal: very short fragments generated during injury act as danger signals, whereas long chains are anti-inflammatory. This is well established in the lab, but there is no evidence of it causing problems from cosmetic topical use, where amounts are small and stay in the dead outer layer.

  Matters most toMostly of scientific interest; people with reactive or inflammatory skin conditions who want to introduce new products one at a time.

Where the EU stands

Sources (3)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy

   Skin Research and Technology · 2016 · doi:10.1111/srt.12228

   Confirmed that 20-300 kDa hyaluronic acid passes the stratum corneum while 1000-1400 kDa hyaluronic acid does not.

2. [2]
   Size Matters: Molecular Weight Specificity of Hyaluronan Effects in Cell Biology

   International Journal of Cell Biology · 2015 · doi:10.1155/2015/563818

   Review establishing that the biological signal from hyaluronan depends on fragment size, with short injury-derived fragments acting pro-inflammatory and long chains acting anti-inflammatory.

3. [3]
   Effectiveness of topical hyaluronic acid of different molecular weights in xerosis cutis treatment in elderly: a double-blind, randomized controlled trial

   Archives of Dermatological Research · 2024 · doi:10.1007/s00403-024-03003-2

   Low molecular weight hyaluronic acid gave higher measured skin capacitance than the high molecular weight version and vehicle, with no difference in water loss or symptom scores and equal safety.