Skin aging is a process that determines the loss of pigmentation. It has been reported that molecules such as Connective Tissue Growth Factor (CTGF) and Transforming Growth Factor Beta (TGF-β) interact each other to establish skin pigmentation. Accordingly, it is hypothesized that the molecular mechanism between CTGF and TGF-β may be described as a reaction-diffusion equation of two generic molecules that produce patterns on the skin. Thus, the reaction-diffusion equations in a two-dimensional domain are used to model skin aging. The Schnakenberg's model with parameters defined in the Turing space was used to simulate the appearance of patterns when the reactive term constantly changes over time. The Finite Element Method is used to solve this equations, while the time was modeled by using the backward Euler approach. It has been found that when the variation between different states of the reactive term progresses at slow speeds, Turing patterns are still obtained. By contrast, when that variation is performed at a higher rate, completely uniform patterns are obtained. Therefore, the reactive term variation can determine the pigmentation (construction and destruction of patterns) during life. This reactive term can be seen as the ability of cells to express the molecules through time.