Skin Surface pH

December 2019 | Volume 18 | Issue 12 | Supplement Individual Articles | 214 | Copyright © December 2019

Charles Lynde MD FRCPC

American Board of Dermatology, Royal College of Physicians and Surgeons of Canada, Department of Medicine, University of Toronto, Toronto, ON, Canada, Lynderm Research, Markham, ON, Canada 

Jerry Tan MD FRCPC

Royal College of Physicians and Surgeons of Canada, Schulich School of Medicine and Dentistry, Department of Medicine, Western University, Windsor, ON, Canada, Windsor Clinical Research Inc., The Healthy Image Centre, Windsor, ON, Canada Sandra Skotnicki MD FRCPC

American Board of Dermatology, the Royal College of Physicians and Surgeons of Canada, Department of Medicine, Divisions of Dermatology, and Occupational and Environmental Health, University of Toronto, Toronto, ON, Canada, Bay Dermatology Centre, Toronto, ON, Canada Anneke Andriessen PhD

Radboud UMC, Nijmegen and Andriessen Consultants, Malden, The Netherlands 

Jennifer Beecker MD CCFP(EM) FRCPC DABD

Royal College of Physicians and Surgeons of Canada, American Board of Dermatology, University of Ottawa, Ottawa, ON, Canada, The Ottawa Hospital, Director of Research, The Ottawa Hospital Research Institute, Ottawa, ON, Canada 

Joël Claveau MD FRCPC

American Board of Dermatology, Royal College of Physicians and Surgeons of Canada, Department of Medicine, Laval University, Quebec City, QC, Canada; Melanoma and Skin Clinic, Le Centre Hospitalier Universitaire de Québec, Hôtel-Dieu de Québec, Quebec City, QC, Canada 

Monica K. Li MD FRCPC

Royal College of Physicians and Surgeons of Canada, Faculty of Medicine, Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada, Enverus Medical, Surrey, BC, Canada and Cosmetic Dermatologist, City Medical Aesthetics Center, Vancouver, BC, Canada 

Jaggi Rao MD FRCPC

Royal College of Physicians and Surgeons of Canada, Division of Dermatology, University of Alberta, Edmonton, AB, Canada 

Jennifer Salsberg MD FRCP

Royal College of Physicians and Surgeons of Canada, University of Toronto, Women’s College Hospital, Toronto, ON, Canada, Bay Dermatology Centre, Toronto, ON, Canada Maxwell B. Sauder MD FRCPC FAAD

Royal College of Physicians and Surgeons of Canada, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, MA, Harvard Medical School, Boston, MA, Toronto Dermatology Centre, Toronto, ON, Canada 

Catherine Zip MD FRCPC

Royal College of Physicians and Surgeons of Canada, Department of Medicine, University of Calgary, Calgary, AB, Canada, Dermatologist, Dermatology Centre, Calgary, AB, Canada

Abstract
The role of skin surface pH, also referred to as “acid mantle,” was described more than 90 years ago and due to developing insights has now returned into focus.1
The role of skin surface pH, also referred to as “acid mantle,” was described more than 90 years ago and due to developing insights has now returned into focus.1 Skin surface pH is influenced by endogenous and exogenous factors such as age, anatomic site, genetic predisposition, ethnic differences, sebum, skin moisture, and sweat production.2-4 Stratum corneum (SC) pH can be documented by measuring pH and buffer capacity of the skin. The pH is a measure of the molar concentration of hydrogen atoms in a solution and describes the acid-alkaline ratio of a substance ranging from the most acidic (0) to the most alkaline (14), with 7 as neutral (Figure 1).5
Physiological skin surface pH is acidic (4–6), while the body’s internal pH is neutral to slightly alkaline (~7.4).5 Buffer capacity is the result of keratinocyte-produced free fatty acids (FFA), and components of (close up space) natural moisturizing factors (NMF), urocanic acid, carbonic acid, and keratins. Buffer capacity is decreased in babies and the elderly.5 Repeat washing with alkaline soap and the use of elevated pH moisturizers reduces buffer capacity.5 Skin surface pH influences skin barrier homeostasis, SC integrity and cohesion, and antimicrobial defense mechanisms.2-4 In inflammatory skin diseases such as atopic dermatitis (AD) and acne, skin surface pH is elevated and therapeutic measures, cleansers, and moisturizers may contribute to deterioration of the condition.5 The current consensus paper explores the influence of genetic and environmental factors on the exacerbation of epidermal barrier breakdown in AD and acne and to what extent these factors attribute to the elevation of SC pH. We further examine the effects of a sustained increase in skin surface pH in these inflammatory conditions, as well as clinical insights into the role of pH and the influence of cleansing and moisturizer use as a measure to sustain skin pH at physiological levels.