The skin dries when it just lacks water. It becomes rough and less flexible. To stay well hydrated, it needs a thin protective layer of fat on its surface, because the fat slows the evaporation of the water. Physiological dry skin, not caused by disease, should be distinguished from pathological dry skin, which is a dry skin due to the symptoms of a disease.
As the temperature rises in the summer, many people are working on the air conditioner. But be aware that air conditioning, just like the sun and pollution, is one of the external factors that affects the skin. It is true that it is a relief to enter a cool place after being in the sun, but spending hours in the air-conditioned room causes more damage to the skin. An air-conditioned room or office is as dry and arid as a desert because the air conditioning sucks in all the moisture. Thus, the dermis loses its moisture, becomes dry, rough and stretches.
The role of collagen and elastin in the aging process is well known. The older the age, the more the skin dries out. It then tends to dry naturally and lose its elasticity. The epidermis has the ability to capture moisture and maintain optimal hydration. But this capacity decreases with age, and skin aging causes a “leakage” of hyaluronic acid, whose role is to capture the water molecules in the epidermis. The drop in hormone secretion that occurs around the fifties is also added to that. Thus, the skin gradually loses its level of hydration.