The stratum corneum is the outermost layer of the epidermis. The stratum corneum is composed of several layers of keratinized cells and contains keratin. Keratin is highly absorbent and generally contains no less than 10% water to maintain skin suppleness; if it is lower than this value, the skin is dry and scaly or cracked. In the pathological state, keratinization abnormalities can be divided into keratosis imperfecta and hyperkeratosis. Let’s take a look at how to self-examine hyperkeratosis. 1.Surface hardening: keratinization intensifies epidermis gradually hardens. 2, loss of luster: local skin keratinization, coupled with sebaceous glands, sweat gland function decline, dry skin, flaking, loss of luster. 3, relaxation and wrinkling: keratinization intensifies the elasticity decline, coupled with subcutaneous fat reduction and other factors, so that the skin relaxation, wrinkles. 4, darkening and yellowing: keratinization intensifies the local antioxidant capacity decreases, epidermal cell division increases, melanin increases and other factors, the skin gradually becomes darker and yellow.