**4. Skin ageing**

Aging is a physiological process that involves the progressive accumulation of changes associated with the passage of time, being responsible for the increased susceptibility to disease and death that accompanies advanced age [5].

Skin aging is particularly important due to its social impact. It is visible and also represents a model organism in which to investigate the aging process. The so-called "biological clock" affects both the skin and the internal organ system in a similar way [6].

We can refer to an intrinsic aging, especially directed by our genome, and an extrinsic aging, determined by a large number of factors, included within the concept of exposome [6].

The term "exposome" was coined in 2005, by the American epidemiologist Christopher Wild, and describes the totality of the exposures to which an individual is subjected from conception to death. It includes both external and internal factors as well as the human body's response to these factors [7].

Skin aging consists of external and internal elements and their different interactions, which as we have said above affect the human being from the moment of conception to death, as well as the human body's response to these factors. As a result of this conjunction, biological and clinical signs of skin aging will appear [6, 7].

The environmental factors that configure the exposome in skin aging are divided into the following categories (**Figure 1**).


*Cosmetic Topical Use of Vitamin C DOI: http://dx.doi.org/10.5772/intechopen.109644*
