The Influence of Calcium on the Skin pH and Epidermal Barrier During Aging

During aging, the pH of the epidermis goes up and the calcium gradient goes down. Both have negative effects on the protective function of the epidermis and both are connected to each other as is discussed here. In the aging process, the pH rises from ∼5 to ∼5.5-6. The establishment of the skin pH is the joint effort of several independent factors including the activity of sodium-hydrogen antiporters and the presence of lactate, urocanic acid, free fatty acids and melanophores in the outermost layers of the skin. All these elements are under the control of a small ion: calcium. Calcium is organized in the form of a gradient in the epidermis with low concentrations in the stratum basale and peak concentrations in the stratum granulosum. During the aging process, this epidermal gradient collapses. In this chapter, we describe how a drop of calcium in the stratum granulosum affects the expression as well as the activity of proteins and enzymes that are involved in the establishment of the skin pH. This rise of the pH combined with a rearrangement of the cornified envelope is a main driver for a reduced epidermal barrier in old age leading to an increased prevalence for infections, reduced resistance against mechanical stress and reduced wound healing.