A number of extrinsic, or external, factors often act together with the normal aging process to prematurely age our skin. They are largely preventable. Most premature aging is caused by sun exposure (photo-aging). Other external factors that prematurely age our skin are smoking, air pollution, unsuitable skin care products, and any severe illnesses.

The ultraviolet light will oxidise the fatty acid chains in the skin, producing the free-radicals. These free-radicals also arise from intrinsic aging process. They are the ultimate culprit for aging of the skin as well as any other body systems. They carry unbalanced electrons, cause direct and indirect damages to the cells.

Normally inside the body there is an enzyme called Superoxide Dismutase, SOD. This enzyme can neutralise the free-radicals and protect from their damages. As we age, more oxidised fatty acid chains accumulate and turn into free-radicals, while less SOD becomes available to fight the battle. Among the extrinsic factors, ultraviolet light and smoking cause the most free-radicals in the skin. The nowadays skin care products very often make emphasis on the ability to counteract these free-radicals, and so their anti-aging properties.