There has been a considerable increase in understanding how skin ages, along with significant progress toward the correction and prevention of the visible signs of aging. However, there are still many unknown factors regarding why we age – and why we all seem to age differently. An area of high interest is the biological or intrinsic processes that affect our appearance over time. This article describes a recent discovery of a membrane bound enzyme proven to be present in skin and increases its activity as biological age increases. The enzyme is located on the external surface of both fibroblast and keratinocytes, and generates free radicals. Therefore, as we age there appears to be a biological mechanism that further increases the production of free radicals. Additionally, there appears to be a relationship between activity of the enzyme and appearance. Data showed that subjects who look younger than their biological age had lower enzyme activity and conversely, subjects who looked older than their biological age had higher enzyme activity. Free radicals are believed to be a major contributing factor in the production of fine lines and wrinkles by destroying the collagen and elastin network keeping skin supple and firm.