**1. Introduction**

The role of ascorbic acid or vitamin C (water-soluble vitamin) in skin health is well known, as we will see later, as early as the eighteenth century its deficit or lack was associated with different skin-type pathologies.

In this chapter, the author, based on the definition of cosmetic products and their economic importance, makes a basic description of the aging process, as well as the anatomy of normal skin and aged skin as an essential basis for understanding the rest of the chapter.

The following sections develop the role of vitamin C in skin health, as well as the different clinical conditions in which it has been shown to be effectively used topically. It includes biochemical bases that allow us to understand, in a simple and practical way, the mechanisms of transport of vitamin C through the different layers of the skin, as well as which are the most effective cosmetic forms that favor its skin absorption.
