Although our understanding of skin barrier function is improving, there has always been a major challenge: how to promote the penetration of active ingredients and cross the skin barrier.
To understand the effect of cosmeceuticals on the skin barrier, we must first understand
- The function and structure of the stratum corneum
- Why the skin become dry
- Environmental effects on the stratum corneum
Functions of the cuticle
The stratum corneum, the first line of defense of our body in contact with the external environment, is a complex multifunctional membrane. Used to retain moisture, gain mechanical strength, selectively transport molecules, and protect against external infections. The stratum corneum is the growth path of skin cells and has a regular growth and metabolism cycle, which eventually forms the final product of the life cycle. The stratum corneum is evolved by the basal cells of the skin, which are regularly shed and renewed.
Why the skin become dry
Properly maintaining and regulating moisture is very important for skin appearance. Strong cleansing, genetic factors, and environmental damage can all damage the skin’s barrier function, leading to cracked skin and a dull and matte dry appearance. Compared with normal skin, dry skin tends to have thicker cuticles, but the skin barrier function is poor.
Environmental effects on the stratum corneum
The stratum corneum is constantly challenged by the external environment, such as temperature and humidity, pathogens, pollution and sunlight UV. All these damage factors can affect the function of the stratum corneum and the appearance of the skin.
- UV damage
As the first part of the body exposed to sunlight UV rays, the cuticle of the skin is also the basic line of defense against the potential damaging effects of UV rays. The skin barrier protects the body from UV radiation. The short-term effect of UV radiation is that it can cause sunburn, and in the long term, it can cause light damage. The stratum corneum provides an effective photoprotective barrier through four mechanisms: the epidermal melanin barrier, the protein barrier, antioxidants, and optical reflection. Ultraviolet rays not only affect the stratum corneum components (cells, lipids, and keratinocytes), but also increase the tendency of the stratum corneum to crack and reduce the skin’s natural ability to resist damage.
- Effects of surfactants
If the skin is exposed to powerful cleansers every day-especially in cold winters-it can take away the proteins and lipids on the skin surface (including the skin emollients / oils on the skin surface and inside), thereby weakening the skin’s barrier function. Powerful surfactants are better able to bind to skin proteins and more easily dissolve and remove lipids and oils. Excessive use of soaps can cause changes in the lipid composition and structure of the stratum corneum, causing dryness.
- Cuticle hydration
Moisturizing is not the most noticeable or exciting effect in skin care products, but it is the effect that most people expect, and various beauty products try to achieve this effect. An effective moisturizing product often has better humectants. The most commonly used glycerin-1 can maintain a certain water content in the stratum corneum; lipid emollients can play a blocking role and prevent the humectants from being washed by water or surfactant Take off. Many moisturizing products can instantly reverse dry skin, leaving the skin soft, smooth and natural-looking. Over time, effective humectants can further restore the elasticity of the stratum corneum, making the skin firmer and more vibrant.
The effective of cosmeceuticals
A typical moisturizer is applied topically to the skin and acts on the surface of the stratum corneum. Theoretically, bioactive ingredients (medicinal and animal products) need to penetrate the stratum corneum barrier and penetrate into the inner layer of the skin to change its biological characteristics to function. Although this effect is limited to a certain level so that they are still considered cosmetics, not drugs. It is not easy to penetrate the skin’s osmotic barrier to reach effective concentrations of targets deep in the skin. How can active molecules penetrate the stratum corneum of the skin? We will discuss current and future strategies in later sections. Researchers are increasingly realizing that in order to improve the overall condition of the skin, it is important to maintain the integrity of the skin barrier and the biological processes associated with its function. Moisturizing products can help restore and maintain barrier function by activating closed functions in dry skin, such as desquamation and hydration. However, based on the latest research progress on stratum corneum-related biology, there seem to be other ways to improve. For example, cosmeceuticals can initiate a signal transduction mechanism that affects the biological processes deep in the skin through the stratum corneum and then activates the biological processes in the epidermis to restore the skin’s homeostasis. Thus, for example, these cosmeceuticals may change the rate of keratinocyte differentiation, improve the composition of lamellar lipid components, and / or increase the breakdown of filaggrin, and the supply of NMF. These features are not found in simple moisturizing products. They can bring some long-term, additional benefits to the skin, and consumers can afford the price.