Skin is the largest organ in our body. It is directly exposed to the outside environment. So it is extremely important in preventing the water loss and the microbial entry. Aging of the skin affected by internal and external factors:
Environment (UV damage, skin cancers, wind, photoaging)
Because of the difference of these factors in different individuals skin age at different rates.
With aging thickness of the skin decreases due to the decreased basal cell layer cell division. This causes to the skin to become more fragile. Collectively this leads to decreased ability to repair the skin, increased irritation to chemicals, increased permeability (may be associated with decrease in the functional barrier??)
In dermis number of collagen fibers and fibroblasts decreases. Remaining collagen fibers make increase number of cross links and cause wrinkling of the skin.
Blood floor to the dermis decreases with the age. This contributes to the pallor of the skin, decreased clearance of foreign material, decreased wound healing ability and decreased inflammatory response.