Sun exposure and hyaluronic acid: good or bad idea?

Some cosmetic actives such as AHA (glycolic acid, lactic acid...) are photosensitising, meaning they can cause detrimental biological effects (redness, hives, itching...) on the skin when exposed to UV, visible or infrared radiation. Depending on the molecules, the mechanisms involved vary slightly, involving or not reactive oxygen species (ROS), produced in excess in situations of oxidative stress. Generally, a photosensitising substance reacts under the effect of the sun to transform into a molecule that deteriorates skin structures and weakens the epidermal barrier, making the skin more sensitive.

Hyaluronic acid is not a photosensitising molecule.

Naturally present in the epidermis and dermis, the hyaluronic acid does not react when exposed to electromagnetic radiation (UV, visible light, infrared). The same applies to the active ingredient incorporated into cosmetic formulations. Therefore, creams and serums containing hyaluronic acid can be applied in the morning without risk, provided they do not contain photosensitising ingredients.

Diminishing wrinkles, enhancing skin radiance, increasing the volume of the lips or certain body parts... Hyaluronic acid injections are currently in vogue and have multiple uses. However, before resorting to them, take the time to thoroughly inform yourself about potential risks and contraindications, for example for pregnant women and people with autoimmune diseases. Moreover, certain precautions before and after the session must be taken. As for sun exposure, it should be avoided the day before the injection, which should be performed on a healthy and non-congested skin. However, there are no contraindications to having hyaluronic acid injections in the summer.

After the session, the patient is advised to avoid sun exposure for the next ten days. There are two reasons for this:

• Even though they do not fall under the category of cosmetic surgery procedures, hyaluronic acid injections are minor traumas to the skin. Consequently, it is not uncommon to see the emergence of bruises and redness, which are fortunately often temporary, following the session. These signs indicate an increased fragility of the skin. More sensitive to external aggressions, including sunlight, the skin must be protected to prevent these marks from becoming permanent.

• Generally, avoiding sun exposure helps to extend the effects of injections, which typically last between 6 and 24 months. Indeed, numerous studies have shown that prolonged, repeated exposure to UV rays alters the structure of the dermis and damages its constituents (DNA, lipids, and also hyaluronic acid). This manifests on a macroscopic level as skin sagging and the early onset of wrinkles and other signs of skin ageing.

• UITTO J. & al. Chronic sun exposure alters both the content and distribution of dermal glycosaminoglycans. British Journal of Dermatology (1996).

• BASENDWH M. A. & al. Complications of hyaluronic acid fillers and their managements. Journal of Dermatologic Surgery (2016).

• THOMAS A. & co. Photosensitisation Reactions of Biomolecules: Definition, Targets and Mechanisms. Photochemistry and Photobiology (2021).

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