Introduction
Skin aging is the result of both intrinsic aging due to the passage of time, and extrinsic aging as a consequence of environmental damage, primarily due to ultraviolet (UV) irradiation.1 The fine wrinkles and reduced elasticity which characterize intrinsically aged skin2 are exaggerated in photoaged skin, with the development of deep wrinkles and a marked loss of elasticity, as well as dryness, roughness, and dyspigmentation.3,4 Wrinkles impair the quality of life for many people due to their perceived unsightly appearance. The demand for cosmeceutical products in the US alone is expected to increase 5.8 percent per annum to $8.5 billion in 2015, driven by an aging population seeking to maintain the appearance of youth.5
In the mid-1990s, the antiaging effects of alpha hydroxy acids (AHAs) were recognized by the cosmeceutical industry leading to a proliferation of AHA-containing