The role of the pH in breaking the skin barrier in Atopic Dermatitis

Abbreviations: AD: Atopic Dermatitis

BACKGROUND

-The Skin barrier is essential in maintaining normal skin
-Increased skin surface pH in the acute phase induces breakdown of the skin barrier.
-In AD the following is found in the upper epidermis

• defective lipid lamella: this results in reduced Natural Moisturizing Factors (NMF), resulting in reduced water retention. Combined with mutated Filaggrin, this contributes to increase the skin pH with the barrier defects due to mutated filaggrin.
• Transmembrane glycoproteins called corneosomes are degraded by enzymes called proteases
• The most superficial layer of the epidermis called the cornified layer (Stratum Corneum) is abnormal.

In summary the following cascade occurs in Skin barrier degradation: low NMF increases the cutaneous pH which increases protease activate which results in increases PAR2 signaling.

How to environmental factors influence skin barrier breakdown ?

• Climate and washing reduce NMF
• Washing and Bodily Secretions increase skin pH

What is the skin surface pH in normal and atopic skin ?

• AD: in the acute phase (pH:7.3), in ongoing AD (pH: 5.7)
• Normal skin: pH around 5.5

Improving the skin pH

• wash with a cleanser to replace harsh soap
• a word on water:
  • living in areas with hard water increases proteases and skin PH, but Williams H showed that there was no benefit to use water softeners.
    In water softeners sodium is replacedby calcium carboonate which increases pH and subsequent breakdown of the skin Barrier.

Skin barrier breakdown and repair in atopic dermatitis. Michael Cork (United Kingdom). SY01 – Atopic Dermatitis. World Congress of Dermatology 2015 –  Vancouver, Canada