Glycerol is a trihydroxy alcohol that has been included for many years in topical dermatological preparations. In addition, endogenous glycerol plays a role in skin hydration, cutaneous elasticity and epidermal barrier repair. The aquaporin-3 transport channel and lipid metabolism in the pilosebaceous unit have been evidenced as potential pathways for endogenous delivery of glycerol and for its metabolism in the skin. Multiple effects of glycerol on the skin have been reported. The diverse actions of the polyol glycerol on the epidermis include improvement of stratum corneum hydration, skin barrier function and skin mechanical properties, inhibition of the stratum corneum lipid phase transition, protection against irritating stimuli, enhancement of desmosomal degradation, and acceleration of wound-healing processes. Even an antimicrobial effect has been demonstrated. Topical application of glycerol-containing products improves skin properties in diseases characterized by xerosis and impaired epidermal barrier function, such as atopic dermatitis. The increase of epidermal hydration by glycerol is critical in skin conditions aggravated by dry and cold environmental conditions, e.g. winter xerosis. This paper provides a review on effects of glycerol on the skin, the mechanisms of its action, and the potential applications of glycerol in dermatology.

Journal Pre-proof J o u r n a l P r e -p r o o f 2 Running title: COVID-19 and the skin Conflict of interests: none Funding sources: none Acknowledgements: none Journal Pre-proof J o u r n a l P r e -p r o o f 3 AbstractThe World has changed dramatically since the COVID-19 pandemic began. Together with our social, occupational, and personal life, the new corona virus poses novel challenges for all physicians, including dermatologists. Despite the virus not being dermatotropic, several skin conditions have emerged, mainly as a result of prolonged contact to personal protective equipment and excessive personal hygiene. Pressure injury, contact dermatitis, itch, pressure urticaria, and exacerbation of pre-existing skin diseases, including seborrheic dermatitis and acne, have been described. We have focused on the dermatologic aspects of COVID-19 infection, so that dermatologist may be aware of the skin complications and the preventive measures to be taken in the COVID-19 pandemic. Abbreviations:healthcare workers -HCWs personal protective equipment -PPE Journal Pre-proof identified as the most common entry for the infection, this includes the conjunctiva with the otic canal having the lowest risk of transmission (4); therefore, specific skin changes due to Covid-19 infection have not been described, and one could expect iatrogenic secondary involvement of the skin.Journal Pre-proof J o u r n a l P r e -p r o o f 5 Because diseases with epidermal barrier interruption could enhance the virus acquisition through indirect contact (5), dermatology patients might be at an increased risk for developing the infection. This suggests that dermatology departments and private offices should develop appropriate preventative measures. (5). Use of a sanitary mask itself may not be sufficient protection from the virus transmission, so that goggles should be used to decrease the risk of conjunctival contamination. COVID-19 has a relatively low-resistance to disinfectants. As a result, a variety of regimens have been proven effective, ranging from 75% ethanol, peracetic acid, chlorine, and UV disinfection to a hot water bath at 56°C(132.8°F) for 30 minutes (4).Another important practical concern is the care for patients with autoimmune and chronic inflammatory disorders, such as psoriasis, atopic dermatitis, lupus, scleroderma, and hidradenitis suppurativa, which may require immune-suppressive therapy. It is not clear whether the administration of the biologics should be delayed. Skin problems related to personal protective equipment (PPE) and personal hygiene measuresThe skin complications in COVID-19 infection are mainly due to the hyper-hydration effect of PPE, friction, epidermal barrier breakdown, and contact reactions, all of which may aggravate an existing skin disease. The dermatologic manifestations are far different from those recorded during the Influenza Epidemic of 1918-1919 (6). Erythema, papules, maceration, and scaling are the most commonly reported skin changes due to extended wear of PPE (6) (figure 1).Symptoms have...

We demonstrated the relation of formation of an acidic pH as well as underlying mechanisms in the induction of a fully hydrated SC over the first weeks of human life as a dynamic functional adaptation.