The effects of hyaluronic acid on brown spots?

Brown spots, or hyperpigmentation marks, correspond to areas of the epidermis affected by an overproduction of melanin and can impact the uniformity of the complexion. Although they can occur in all skin tones, they are generally more common in darker phototypes (IV to VI) and tend to appear around 40-50 years of age. Most often, pigmentation spots result from repeated and prolonged sun exposure throughout life. Hormonal variations, particularly in pregnant women, can also cause hyperpigmentation: this is the well-known pregnancy mask. Finally, increased activity of melanocytes stimulated by pro-inflammatory cytokines can also cause brown spots. This is referred to as post-inflammatory hyperpigmentation.

While certain active ingredients can act against hyperpigmentation and reduce it, there is currently very little scientific evidence indicating that this is the case for hyaluronic acid, whose cosmetic power lies mainly in its ability to absorb and retain water. As for its potential depigmenting effects, these have not been the subject of any clinical trials. Only one study, conducted very recently in vitro on human skin explants, has looked into this. For this, a molecular complex composed of high molecular weight hyaluronic acid, amino acids (cysteine, glycine, lysine, proline, and valine), oligopeptides (glutathione), vitamin C, and biotin was tested.

This complex was administered to certain skin explants and the percentage of cells exhibiting low, medium, and high levels of melanin was evaluated as an indicator of the degree of pigmentation. The results obtained are recorded in the table below and show a depigmenting action of the complex.