The acidic character of skin was rst mentioned by Heuss [1] and later by Schade and Marchionini [2], who introduced the term “acid mantle” for skin’s acidic outer surface pH. The importance of skin’s acidic character has been recognized as playing a crucial role in permeability barrier homeostasis, skin integrity/cohesion, and immune function [3-5]. Given the importance of the acidic skin pH for normal function and defenses, it is important for skin to be able to resist acidic/ alkaline aggression to some extent (i.e., have buffering capacity) [6]. As we age and in skin disease, the baseline skin pH can increase, and our ability to buffer the change in skin pH can decrease [7]. This increase in pH and impaired skin buffering capacity can lead to dysfunctional barrier homeostasis and skin integrity/cohesion, increased likelihood for skin infection, and increased sensitivity/irritation to topically applied products [8].