Why does the skin need to be hydrated?

Previously, people generally regarded endocrine disorders and other factors as the fundamental source of skin aging, but they did not know that water deficiency was the culprit of skin aging. When the moisture content of the surface layer of the skin, namely the stratum corneum, reaches 15-25% and is sufficient, the skin will not only be soft and smooth without fine lines, but also be full of elasticity in the feel; But with age and unhealthy lifestyle, the moisture in the stratum corneum gradually loses. When the content is below 10%, the skin will appear dry, fine lines, tightness, roughness, and eyebrow detachment. Although the surface layer of the skin cannot directly obtain moisture from the inside of the body, there is a constant flow and supply of moisture in the lower dermis of the skin. So, skin hydration is fundamentally about replenishing the moisture in the dermis from the source. Moisturizing the dermis is the first element of skincare, and whitening, oil control, wrinkle resistance, and aging should all be carried out on this basis.