Seasonal variations in the skin parameters of Caucasian women from Central Europe.

BACKGROUND: The human skin is greatly affected by external factors such as UV radiation (UVR), ambient temperature (T), and air humidity. These factors oscillate during the year giving rise to the seasonal variations in the skin properties. The aim of this study was to evaluate the effect of seasons, environmental T, relative and absolute humidity on the skin parameters of Caucasian women, perform a literature review and discuss the possible factors lying behind the found changes. MATERIALS AND METHODS: We measured stratum corneum (SC) hydration, transepidermal water loss (TEWL), sebum level, erythema index, and elasticity parameters R2 and R7 on the forehead and the cheek of Caucasian women from the Czech Republic throughout the year. We also performed a non-systematic literature review focused on the seasonal variations in these skin parameters. RESULTS: We confirmed a well-documented low SC hydration and sebum production in winter. In spring, we found the lowest TEWL (on the forehead) and the highest SC hydration but also the highest erythema index and the lowest elasticity presumably indicating skin photodamage. For most of the skin parameters, the seasonal variations probably arise due to a complex action of different factors as we extensively discussed. CONCLUSION: The data about the seasonal variations in the skin parameters are still highly inconsistent and further studies are needed for better understanding of the normal skin changes throughout the year.

A new unsaturated derivative of hyaluronic acid - Synthesis, analysis and applications.

Hyaluronic acid (HA) containing CC double bond in positions 4 and 5 of N-acetyl-glucosamine ring (ΔHA) is an unique material, which could be used for biomedical applications and cosmetics. The main advantage of the CC double bond is its ability to react with a wide range of oxidation agents. Location of the CC double bond directly on the glucopyranose ring allows to change the chemical capabilities and simultaneously to mimic the intrinsic physical properties of HA without introduction of linkers or other substances. The synthesis, structural analysis and basic chemical and biological characteristics of this novel biopolymer are described in details. In vitro cytotoxicity assays showed selective activity of ΔHA against cancer cell lines in comparison with standard human fibroblasts so this material has great potential in the field of anticancer drugs.