It has to do with cutaneous senescence . With age, the sweat glands need more and more outside temperature to function, which makes the elderly sweat less.
On the other hand, with aging the outer layer of the skin (epidermis) thins. Aging skin also loses color and pales as the number of pigment-containing cells (melanocytes) decreases. In addition, the blood vessels in the dermis become more fragile, leading to bruising, bleeding under the skin, capillary hemangiomas, and similar conditions. And the sebaceous glands produce less oil when we add years, causing moisture loss, dryness and itchiness.
Added to this is that, over time, the defense system of the skin tissue becomes disturbed and becomes unable to attract T lymphocytes to keep possible invaders at bay. That explains why we are more vulnerable to infections and skin cancers in our 70s than, for example, in our 40s.
