All this leads to physiological

Extrinsic factors include ultraviolet (UV) radiation (which contributes up to 80% to the aging process), pollution, ionizing radiation, smoking, sleep patterns, sleeping position, as well as the use of chemicals and toxic All this leads to physiological and structural alterations in each layer of the skin and in its appearance.

One of the main extrinsic factors is photodamage. UV rays (Night Comfort Review) generate free radicals that increase the activity of collagenase (through the epidermal growth factor receptor (EGFR).

Increasing the fragmentation of collagen and decreasing the transforming growth factor beta (TGF-β) , which in turn decreases the formation of collagen fibers. This has been demonstrated histologically in vivo with increased levels of messenger RNA (Night Comfort Review) of collagenase and increased activity after uv exposure, and decreased expression of the procollagen I after this same exposure.