The key to hair health lies in the nutrition of scalp subcutaneous tissue. As mentioned earlier, collagen located in dermis is a nutritional supply station for epidermis and epidermal appendages (mainly hair and nails). Lack of collagen, dry hair and split nails are easy to break and dull.
Hair itself, like skin, is composed of collagen. Cross-cutting a hair can be seen under the microscope: the center is hair pulp, the middle is collagen, and the outermost layer is hair scale. Collagen mainly controls the roughness, elasticity and wettability of hair. Hair scale is a very fragile tissue, which will be worn when rubbed and heated, and the collagen in the inner layer will be stimulated and decomposed.
Therefore, if you want to have a beautiful hair, you can't just do superficial things, you need to treat the symptoms. The cure is to supplement collagen and nourish subcutaneous tissue, thus promoting the health of hair and nails and keeping them soft and shiny.