The primary factor of extrinsic ageing is UV radiation. Research shows that approximately 80% of all symptoms of premature skin ageing are caused by UV exposure while all structural components of the skin are damaged by chronic sun exposure.
UV-A rays are primarily responsible for photoaging, but high-energy visible light (HEV) can also cause oxidative stress that damages the skin at a cellular level. As a result of the damage, signs of ageing begin to form such as wrinkles, volume loss, skin sag, and pigmentation.
UV-B rays are absorbed by skin cells and cause direct damage to cellular DNA.