This set of experiments consisted of three parts:

Firstly, four different molecular weights of hyaluronic acid (20kDa, 50kDa, 130kDa, and 320kDa) were selected and their effects were observed in terms of causing skin inflammatory reactions in pig ear skin. It was found that 20kDa significantly caused the inflammatory response in the skin. The ability of hyaluronic acid with a molecular weight of 50 kDa to cause an inflammatory response was much lower than 20 kDa and lower than 130 kDa, thus ruling out the possibility of using 20 kDa as a safe ingredient in skin care products.

The second set of experiments investigated the penetration of hyaluronic acid of different molecular weights into the skin of pig ears. It was found that the penetrating power of hyaluronic acid at 50kDa was much higher than that of hyaluronic acid at molecular weights above 300kDa.

The third group of experiments confirmed the effect of different molecular weights on skin wrinkles (anti-wrinkle effect). The results are shown below, and it is clear that 50kDa has the most pronounced anti-wrinkle effect. The article concluded that the molecular weight of hyaluronic acid can be chosen to avoid the inflammatory response of the skin caused by low molecular hyaluronic acid. Hyaluronic acid above 50 kDa has the best anti-wrinkle effect. Other large molecular weights of hyaluronic acid do not penetrate the skin well enough to be biologically effective.

In practice, it is extremely difficult to achieve a single molecular weight for hyaluronic acid used as an ingredient in skincare products, and most of these ingredients are within a range of molecular weights, which means they are all mixtures of different molecular weights. On balance, I still prefer hyaluronic acid in the 50kDa-110kDa molecular range the most. The penetration is not bad, the safety is high, and the effect is reliable. So when our company makes formulations, the low molecular hyaluronic acid ingredients are also in this range.

We can look at it this way, hyaluronic acid itself is a huge multimer, and the reason why it has a good moisturizing ability is related to its molecular weight. The higher the molecular weight the better the moisturizing ability, but the lower the penetrating ability.

The ultra-low molecular weight hyaluronic acid does not have such a good moisturizing ability. So there is no scientific basis for trying to achieve deep moisturizing with such ultra-low molecular hyaluronic acid. And the presence of such ultra-low molecular weight hyaluronic acid in the deeper layers of the skin may instead lead to inflammatory reactions in the skin through information transfer. It should be avoided as an ingredient in skin care products.

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