How do high vs low molecular weight hyaluronic acid compare?Updated a year ago
So how do high vs low molecular weight hyaluronic acid compare? And what about mixed-HA formulas? Here are the key differences.
The molecular weight in numbers
Depending on how it’s produced and manipulated, the molecular weight of hyaluronic acid can vary very widely, as can its penetration:
- Low molecular weight HA has between 20-300 kilodaltons
- Medium weight is between 300-1000 kilodaltons
- High weight has between 1000-1400 kilodaltons
Penetration
Low molecular weight hyaluronic acid has become more popular in recent years because of its greater depth of absorption. Research shows that low molecular weight HA can penetrate down to the bottom of the epidermis.
By comparison, medium-weight HA penetrates only to the center of the epidermis, while high molecular-weight HA only permeates the stratum corneum, which is the outermost layer composed exclusively of dead cells.
Many believe that low molecular weight hyaluronic acid is better because it can penetrate more deeply. After all, isn’t it better to have more hyaluronic acid throughout the epidermis?
In reality, the level of skin most impacted by dryness and dehydration is the stratum corneum. It’s our body’s last little layer of defense against the outside world, and it’s also the last level of skin to receive any moisture or nutrients from the body. When it’s dry and dehydrated, it can crack or become rough. This makes the skin feel uncomfortable and can potentially allow for bad pathogens to penetrate through and damage the skin.
Risk of irritation
As a rule, the more deeply an ingredient can penetrate past the stratum corneum, the more likely it is to induce irritation. And indeed, low molecular weight hyaluronic acid has been found to have a pro-inflammatory effect.
Our body produces hyaluronic acid as part of the wound-healing process, setting off the inflammatory cascade that ultimately leads to healing. However, in healthy skin, some users may experience irritation.
It seems that irritation is likeliest when using several products with hyaluronic acid within one routine, especially with low or mixed molecular weight hyaluronic acid formulas. This effect hasn’t been documented in medical or scientific literature yet, but within the skincare community, there have been a lot of incidences reported by enthusiasts, influencers, and even dermatologists.
High molecular weight hyaluronic acid has an anti-inflammatory effect, by contrast. While this effect hasn’t been measured topically in human skin, we suspect that high molecular weight HA is significantly less likely to irritate, even with consistent use.
Anecdotes aren’t data, but at least within our lab team, those with sensitive skin have not had any issues using our Hyaluronic Acid & Niacinamide Hydration Cream over long periods.