Ideal protection vs. actual protection

Sun exposure is appreciated for its effect on morale and also because it allows for the epidermal synthesis of vitamin D. But its dangers are also increasingly known. “UVs are responsible for many biological effects both beneficial and harmful to the body. At the cellular level, UVs act at the nuclear, membrane, and cytoplasmic level,” explained Professor François Aubin (University of Franche Comté). UVAs, which represent 95% of the spectrum, are the ones with the deepest penetration into the skin.

More recently, the effects of near infra-reds on photo-induced skin ageing have been highlighted. “50% of free radicals are produced in the visible and near infra-red. These wavelengths between 760 and 1400 nm impact the dermis at high doses causing the metalloproteinase-1 over-expression in dermal fibroblasts,” underlined Jürgen Lademann (Charity Universitätsmedizin Berlin). Lademann also evidenced that near infra-reds regulated highly influential genes in skin homeostasis. He therefore advocated for a protection across the whole light spectrum range and not only centred on UVs.

Providing formulations with a UVA and UVB protection is already a requirement. “The product’s dosage form plays an important role, it will determine the amount of product to apply. It is shown that products that spread easily are associated both with a low variation of SPFs and a positive sensory evaluation, which leads, in turn, to the application of a larger amount of lotion,” noted Marc Pissavini (Coty Lancaster), while observing that people always remained below the 2mg/cm² mark required by the standard methods of assessment for the determination of the sun protection factor. Pissavini therefore recommended for the use of an “in vivo veritas SPF” that would take into account the product’s absorbance spectrum, its uniformity of application and the amount of product applied to actually come closer to an "in vivo on-the-beach-use”.

Photo-biomodulation or the light that heals

In contrast, certain wavelengths in the visible spectrum are also used as therapeutic means. According to Dr. Pelletier (European LED Academy Society) “photo-biomodulation, which is the process by which chromophores are absorbed by selective wavelengths leading to major signalling phenomena for biological cellular synthesis, is part of the modern management for a successful ageing.

Clinical studies have highlighted the interest of red light in stimulating melanocyte proliferation and differentiation in cultures. “More recently, it was demonstrated that blue visible light was able to induce in people with a high phototype, a more intense and lasting hyperpigmentation than that obtained with UVAs,” highlighted Professor Thierry Passeron (CHU Nice). Light therefore is of great interest to treat pigmentation disorders such as vitiligo, scars, stretch marks, acne.

Meanwhile, Jean-Alexis Grimaud, (University Paris VI), founder and Research Director of the Matriscience Company proposes a screening method for active ingredients subjected to LED illumination. “Our method enables to revisit under the angle of photo-biomodulation known molecules whose activity could therefore be optimized”.

Many research fields that open interesting cosmetic perspectives.

Young researchers are recognized

For the first time, the organizers of the Journées Jean-Paul Marty invited young researchers to present their work and compete for the best poster Award. Élodie Gibert (laboratoire de Pharmacie Galénique Industrielle de l’Université de Lyon 1) was recognized for her work on the measurement, analysis and prediction of the absorption of chemical UV filters in the stratum corneum.