Parents are always looking at getting the right product for their children with eczema – many of these are marketed as pH-balanced and it can be confusing whether alkaline, acidic or neutral is good.
We are privileged to have Cheryl Lee Eberting, M.D. to help answer our questions in this 5-week skin pH series. Cheryl Lee Eberting, M.D. is a Board Certified Dermatologist and a past clinical research fellow of the National Institutes of Health. Dr. Eberting invented the TrueLipids skin barrier optimization and repair technology; a technology that helps the skin to repair itself by recreating its own natural environment.
What is our Skin pH?
pH stands for the potential of hydrogen, which is a measurement of the hydrogen ion concentration. pH scale ranges from 1 (most acidic) to 14 (most alkaline) with 7 representing neutral. The skin pH comes from the ‘acid mantle’, which is an emulsion of secretions from sebaceous (oil) and sweat glands and decomposed corneocytes (upper skin layer cells).
MarcieMom: Dr Cheryl Lee, this acid mantle on the surface of the skin is what gives the skin its pH level. However, the optimal pH of the skin barrier seems to change with more studies being conducted. I understand that the ideal pH of the skin barrier is thought to be 5.5, but it is now accepted as being more acidic from 4.5 to 5.0.
Dr Cheryl Lee: You are right about the great variation in the ideal skin pH in the medical literature. When you read the skin pH literature, there seems to be a range of between 4.6 to 5.6 depending on the study and where on the body the pH was tested. Dermatologists do agree that the skin should have an acidic pH somewhere in this range. When our skin comes in contact with alkaline substances such as soap or even tap water, the optimal pH is exceeded. Tap water has been shown to alkalinize the pH of the skin for six hours. This means that the natural buffering systems in the skin barrier take up to six hours to buffer the skin barrier back into the optimal acidic range when the skin comes in contact with tap water. Soap and bleach are even more alkaline than tap water and obviously have an even more dramatic effect on alkalinizing the skin barrier.
Why is More Acidic Skin pH the ‘Ideal’?
Dr Cheryl Lee: The epidermis is composed of the epidermal lipid barrier which contains many lipids (fats) that serve to keep the skin water proof, infection-proof, chemical and allergen proof and much more. These epidermal lipids are composed of four main classes including Ceramides (47%), cholesterol (24%), fatty acids (11%), and cholesterol esters (18%). The ceramide fraction is a very important part of the lipid bi-layer that lines the corneocytes in the epidermis. We know that ceramides are important for preventing water loss, infection, irritation and in helping to regulate the pH as well. The main enzymes that make ceramides are called B-Glucocerebrosidase and acid sphingomyelinase. Both of these enzymes have an optimal pH in which they can do their work and produce ceramides. If the pH of the skin exceeds about 5.7, then there are other enzymes(serine proteases) that become activated in the skin and will literally chop up and metabolize the ceramide-producing enzymes rendering the skin unable to make skin barrier lipids and to repair itself. As the skin barrier lipids can no longer be replenished, then the skin barrier begins to break down. Thus, we learn how ceramide production can come to a halt and affect the integrity of the skin barrier when the pH of the skin is too alkaline.
Ceramides are important for preventing water loss, infection, irritation and in helping to regulate the pH as well.
Optimal Skin pH and Good/Bad Bacteria Skin Colonization
Another important facet of the optimal pH of the skin is the role it plays in the skin’s microbiome. The term microbiome describes all of the good and bad bacteria that live on our skin. An acidic pH discourages the growth of bad bacteria and encourages the growth of good bacteria. Staph. aureus for example, prefers a more alkaline environment and does not like to grow in the normally acidic environment of the healthy skin barrier. Good bacteria like Staph. epidermis prefer the acidic environment and do not thrive in an alkaline environment. As you may know, people who have atopic dermatitis are particularly susceptible to the overgrowth of Staph. aureus. This has a lot to do with the overly alkaline environment of the skin barrier AS WELL AS the particular lipid deficiencies that are present in atopic dermatitis.
Acidic pH discourages bad skin bacteria growth
Skin Barrier Lipids are Naturally Anti-Staphylococal
The skin barrier in atopic dermatitis has been shown to have particular lipid deficiencies. For example, there are well-documented deficiencies in phystosphingosine, phystosphingosine-containing ceramides like Ceramide 3, in cholesterol esters (NOT CHOLESTEROL) and in Very Long Chain Fatty Acids. Phytosphingosine for example, has been shown to have anti-staphylococcal and anti-candidal effects and has been shown to be deficient in aged, dry and eczema-prone skin. Phytosphingosine deficiency leads to the phytosphingosine-containing ceramide deficiency. These ceramides are produced by the pH dependent enzymes and are not produced at appropriate levels in atopic skin. This contributes to the colonization/infection by Staph. aureus and becomes part of the wicked cycle that we all know in atopic dermatitis. You can see, this is a very interconnected cycle of lipid deficiency, alkaline pH, infection….repeat. We can attempt to break the cycle by addressing all of these things simultaneously.
Thank you Dr Cheryl Lee in explaining the importance of skin pH; next week, we will learn more about what happens in off-optimal pH skin.