How to choose a good hyaluronic acid?

The hyaluronic acid is a molecule found in the dermis, eyes, muscles, and even joints that has the characteristic of being hydrophilic. Acting like a sponge, it retains about 1000 times its weight in water. In addition to its strong hydrating power, the hyaluronic acid has healing and anti-inflammatory virtues, making it a choice active ingredient in cosmetic formulation. It is included in the composition of many skincare products under several INCI names: Hyaluronic Acid, Hydrolysed Hyaluronic Acid, Sodium Hyaluronate, Sodium Hyaluronate Crosspolymer... These different forms of hyaluronic acid have slightly different properties, particularly due to the difference in molecular weight of the active ingredient, making the choice of a product delicate.

Indeed, low-molecular-weight hyaluronic acid (50 - 1000 kDa) is able to penetrate deep into the epidermis, where it can act as a signalling molecule for the synthesis of new endogenous hyaluronic acid molecules. It thus promotes hydration of cutaneous tissues and structural maintenance of the extracellular matrix. It is recommended for those wishing to prevent or attenuate the signs of ageing. High-molecular-weight hyaluronic acid (> 1800 kDa) remains on the surface of the stratum corneum, where it ensures hydration of the superficial layers of the epidermis and limits water loss. It is particularly appreciated by dehydrated skin, giving it a plumped, smooth appearance, even if this effect is temporary.

A recent study compared the effects of different formulations of hyaluronic acid with varying molecular weights. Over a period of 60 days, 76 women with wrinkles around the eye contour applied a 0.1% hyaluronic acid cream twice daily at 50, 130, 300, 800, or 2000 kDa. The progression of various skin parameters was measured. The results are presented in the table below.

Upon reviewing this report, it appears that the active ingredients that have achieved the best overall results are hyaluronic acid at 130 kDa and that at 300 kDa. The study thus seems to suggest that low molecular weight hyaluronic acid offers more interesting cosmetic possibilities.

However, to maximize the benefits, it is generally recommended to combine high molecular weight hyaluronic acid with low molecular weight hyaluronic acid in cosmetic formulation, the ideal being to have a 50:50 ratio.

Note : Regarding injections, the preferred type of hyaluronic acid is the cross-linked form, meaning it has a three-dimensional structure. This cross-linking allows for an extended duration of the hyaluronic acid's effect because it makes it more resistant to enzymatic degradation. In aesthetic medicine, hyaluronic acid injections are primarily used to fill in wrinkles, increase lip volume, redefine facial contours, and restore lost volume.

• ANDRE P. Hyaluronic Acid and Its Application as a "Rejuvenation" Agent in Cosmetic Dermatology. Seminars in Cutaneous Medicine and Surgery (2004).

• PAVICIC T. & al. Effectiveness of cream-based new formulations of hyaluronic acid of varying molecular weights in anti-wrinkle treatment. Journal of Drugs in Dermatology (2011).

• DAYAN E. & al. Practical Approach and Safety of Hyaluronic Acid Fillers. Plastic and Reconstructive Surgery (2019).

• SINKOROVA Z. & al. Hyaluronic Acid: Recognized for Nearly a Century, Yet Still Trending. Pharmaceutics (2022).