Rosacea: Green algae to reduce the visibility of blood vessels on the skin?

Diffuse redness is one of the ways in which rosacea manifests itself on the face. They are the result of the dilation of small, fine blood vessels on the skin's surface, which are red or purplish in colour, known as telangiectasias . Several factors can promote their appearance, such as heat, spicy food or stress.

Indeed, thegreen algae is said to be capable of neutralising the colour red. This is because it contains green photosynthetic pigments known as chlorophyll. Based on the colour wheel, we can see that red and green are located opposite each other: they are therefore complementary. When two complementary colours are mixed, their hues cancel each other out.

Applying a compound containing green pigments, such as green algae, topically, in complexion correctors for instance, would then "cancel out" the red colour of redness associated with the dilation of blood vessels in the context of rosacea.

Angiogenesis is the process of forming new blood vessels. In the context of rosacea, there is an accelerated growth of new blood vessels, causing them to enlarge, spread their roots, and become more visible on the skin's surface.

In a study conducted in 2007, Pierre-Yves MORVAN aimed to verify the effects of Chlorella vulgaris, a green algae, on angiogenesis using an in vitro model composed of human endothelial cells co-cultured with human fibroblasts. The effect of C. vulgaris was studied by measuring the length of the tubules. C. vulgaris at 0.1% significantly reduced the length of the vessels by -46% compared to the control.

C. vulgaris could therefore be of interest for skin conditions related to redness and telangiectasias such as rosacea. One of the mechanisms involved could potentially be the inhibition of angiogenesis. The author hypothesises that this effect could be the result of a reduction in the action of the vascular endothelial growth factor (VEGF), responsible for angiogenesis, through the overexpression of the metalloproteinase-3 inhibitor (TIMP3), which is an antagonist of the VEGF receptor.

Nevertheless, these remain hypotheses to be considered with caution. Only this study has demonstrated these effects and the model used is in vitro. Additional data would help to clarify these results.

In the same study, Pierre-Yves MORVAN then turned his attention to the impact of C. vulgaris on vascular imperfections, which are more visible in cases of rosacea. Seventeen women applied a cream containing C. vulgaris at 1% twice a day for 84 days. The volunteers had visible lesions associated with venous dysfunction: small varicose veins, small spider angiomas and telangiectasias.

The effect of the product on varicose veins was assessed after 28 and 84 days of application. C. vulgaris at 1% visibly reduced the redness of vascular lesions: -15% on average and up to -64% after 28 days of use; -25% on average and up to -77% after 84 days of use. The treatment improved the size and colour of the vascular lesions.

The inhibition of angiogenesis by C. vulgaris previously observed could also be responsible for this visible reduction in vascular lesions. The author also cites another potentially involved mechanism. In this study, the scientist noted that C. vulgaris at 1% increased the expression of collagen I (+333%) and III (+150%) by human fibroblast cultures in an in vitro experiment.

It has been previously demonstrated that collagen has the ability to strengthen the walls of veins and that a deficiency in this protein has been linked to the development of varicose veins. Weakened and less elastic venous walls would lead to the accumulation of blood in the vein, which eventually stretches it to the point where it widens and becomes more visible. Collagen would then form a sort of "sheath" around the vascular lesions, which reduces their appearance.

Once again, these effects have only been demonstrated once, and further studies are essential to confirm these results.

• VERBEUREN T. J. & al. Chronic venous insufficiency: dysregulation of collagen synthesis. Angiology (2003).

• MORVAN P. Y. Effect of Chlorella extract on skin. Personal Care (2007).