Skin hydration, also referred to as skin moisture, is a widely used term. But exactly what is behind it and why is it such a crucial component of the skin’s wellbeing?
A major function of skin is the prevention of excess water loss by means of an epidermal barrier. The skin’s moisture level influences not only the microscopic parameters, such as protein activity and intercellular signaling, but also macroscopic, or visible, aspects such as the elasticity and suppleness of the skin (1).
Chemically speaking, hydration denotes the arrangement of water molecules to create a protective hydration shell through the formation of hydrogen bonds. This envelope offers protection from factors such as environmental stressors and noxious agents, among others, that could damage the skin.
Moisture can leave the skin by evaporating off the skin’s surface through perspiration, but this process is limited. The skin possesses a multitude of regulatory mechanisms to keep the upper layer, known as the stratum corneum, adequately supplied with moisture.
Furthermore, good skin care can significantly reduce the amount of water lost and thus increase the moisture content of the skin. The skin-lipid barrier plays a vital role in the hydration process. Intercellular lipids (lipids located between cells) store moisture by using their water repelling properties to reduce the amount of water lost to evaporation.
There are various active ingredients capable of improving the skin’s moisture by specifically strengthening the skin-lipid barrier. One example is almond oil, a product used in ancient Chinese, Ayurvedic, and Greek medicine (2). In one randomized, double-blind study, the application of lactic acid and refined almond oil, both with and without polidocanol (an antipruritic agent), led to a significant reduction in itchiness and an increase in the skin’s lipid content (3).
Another class of ingredients shown to improve skin moisture and elasticity are aloe vera extracts. One particular study showed that a moisturizing cream containing aloe vera extracts, as well as wheat germ oil and other herbal ingredients, provided a measurable hydrating effect when participants applied the cream twice daily for three weeks (4).
There exist various topical preparations with various active ingredients. For long-lasting hydration, note the following important points: