Atopic Eczema: Skin Barrier Strengthening and pH

Skin is not just a dead layer. In the previous post, I discussed skin barrier function and pH conditioning. In this post, we will delve deeper into the role of pH in the skin barrier.

Since various enzymes have different optimal pH levels for proper function, it can be understood that pH can partially act as an on/off switch for various functions.
Source: Fluhr, J. W., & Darlenski, R. (2018). Skin Surface pH in Newborns: Origin and Consequences. Current Problems in Dermatology, 26–32. doi:10.1159/000489515

The epidermis exhibits a biphasic pH gradient structure. These pH changes partially explain the functional differentiation within each layer.

Skin pH precisely regulates various functions. Next, it would be meaningful to examine what supports this pH. You can find relevant information by searching for "skin acidification."

Factors Contributing to Skin Acidity

Factors that contribute to skin acidity are broadly categorized into endogenous and exogenous factors.

• Exogenous Factors: sebum-derived free fatty acids (FFAs), bacterial metabolites, eccrine gland-derived lactic acid
• Endogenous Factors: sPLA2, NHE-1, histidine-derived components

The process of FFAs being supplied from phospholipids also seems to be one of the important topics discussed in relation to pH.
Source: Generation of Free Fatty Acids from Phospholipids Regulates Stratum Corneum Acidi®cation and Integrity

In summary, skin acidity is very precisely regulated, and the factors supplying skin acidity can be understood as multifactorial.

Source: Fluhr, J. W., Darlenski, R., Lachmann, N., Baudouin, C., Msika, P., De Belilovsky, C., & Hachem, J.-P. (2012). Infant epidermal skin physiology: adaptation after birth. British Journal of Dermatology, 166(3), 483–490. doi:10.1111/j.1365-2133.2011.10659.x

Since the process of skin pH acidification is highly multifactorial, it would be difficult to condition this intricate process by applying acids externally. The reason why mildly acidic cleansers are considered important is that conventional alkaline soaps or cleansers act as factors that disrupt the already precisely adjusted pH gradient.

We will discuss skin pH in more detail later if necessary, and conclude here for now.