Is hyaluronic acid irritating?

A star ingredient in anti-ageing treatments, hyaluronic acid is ubiquitous in cosmetics. Naturally present in the human body, this extremely hydrophilic glycosaminoglycan primarily functions to ensure the hydration of the skin. At the dermis level, it helps to form its connective tissue and serves as a support to collagen and elastin fibres. It thus plays a fundamental role in the density and firmness of the skin. The hyaluronic acid found in cosmetics comes in several forms, notably characterised by their molecular weight. Indeed, depending on its degree of cross-linking, this active ingredient can be of high (> 1800 kDa), medium (1000 - 1800 kDa) or low (50 - 1000 kDa) molecular weight. Generally, the smaller the size of a molecule, the deeper it can penetrate into the epidermis.

Low-molecular-weight hyaluronic acid is often suspected of being irritating, due to its high absorption capacity by the skin. While it's true that skin sensitivities vary from one individual to another, and that some people have difficulty tolerating topical hyaluronic acid, they are far from being in the majority. Hyaluronic acid is a cosmetic active ingredient that is generally well tolerated, and is even used in ophthalmology for both conservative and operational purposes. Hyaluronic acid is also used in wound-healing products to reduce irritation. In a recent study, 43 people with wounds were given a dressing containing 0.05% hyaluronic acid or a 0.2% cream. After 10 days' use, all saw an improvement in their wounds, which had reduced by an average of 70%.

Several studies, conducted with both men and animals, have demonstrated the safety of using hyaluronic acid. Notably, recent research involving 15 volunteers aimed to investigate the potential irritant effect of this active ingredient. Patch tests of different serums containing 0.5, 1 and 2% of low molecular weight hyaluronic acid (400 kDa) were carried out on the participants' forearms. No irritation was observed after 30 minutes, 72 hours, 96 hours and 1 week.

However, as mentioned earlier, even though hyaluronic acid does not fall into the category of irritating actives, this does not prevent some individuals from developing redness or itching after applying a product containing it. This is why we advise you to always perform a tolerance test after purchasing a new product, regardless of the active ingredient it contains. Easily achievable, you simply need to apply a few drops of the product to the inside of your elbow or wrist, wait 24 hours, and observe for any tingling, swelling, or redness.

Note : Hyaluronic acid injections pose a greater risk of irritation than topical application. Although this active ingredient is biocompatible and biodegradable, there is no such thing as zero risk and several cases of redness, swelling and inflammation have been reported.