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CME #114 – March 2003 The Importance of Skin pH

CME #114 – March 2003 The Importance of Skin pH

Introduction Skin & Aging is proud to bring you this latest installment in its CME series. This series consists of regular CME activities that qualify you for two category one physician credit hours. As a reader of Skin & Aging, this course is free for you — you aren’t required to pay a processing fee. Skin pH is a very important issue, and though it’s typically neglected by U.S. home-care companies, it’s an issue about which you and your patients should be aware. Many skin and systemic diseases can affect pH levels, as can products, such as soaps and moisturizers, which we all use everyday. At the end of this article, you’ll find a 10-question exam. Mark your responses in the designated area and fax page 93 to HMP Communications at (610) 560-0501. About 1 month after the publication date, we’ll post this course on Skin & Aging’s Web site, which you can access at www.skinandaging.com. I hope this CME contributes to your clinical skills. Cordially, Steven R. Feldman, M.D., Ph.D. CME Editor Dr. Feldman is Associate Professor of Dermatology and Pathology at Wake Forest University Medical Center in Winston-Salem, NC, and Professor of Dermatology and Director of the Bristol-Myers Squibb Center for Dermatology Research. Principal faculty: Gil Yosipovitch, M.D., and Judy Hu, M.D. Method of Participation: Physicians may receive two category one credits by reading the article on pages 89 to 92 and successfully answering the questions found on p. 93. A score of 70% is required for passing. Fill out the last page and submit your answers and evaluations via fax or log on to www.skinandaging.com and respond electronically. Estimated time to complete the educational activity: 2 hours Dates of original release: March 2003 Expiration Date: March 2004 This activity has been planned and produced in accordance with the ACCME essentials. Accreditation Statement: HMP Communications, LLC, is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. Designation Statement: HMP Communications, LLC designates this continuing medical education activity for a maximum of two category one credits toward the AMA Physician’s Recognition Award. Each physician should claim only those credits that he/she actually spent in the educational activity. Disclosure Policy: All faculty participating in continuing medical education programs sponsored by HMP Communications are expected to disclose to the meeting audience any real or apparent conflict(s) of interest related to the content of their presentation. Faculty Disclosures: Drs. Yosipovitch and Hu have disclosed that they have no significant financial relationship with any organization that could be perceived as a real or apparent conflict of interest in the contexts of the subject of their presentation. Learning Objectives: At the conclusion of this educational activity, the participants should be able to: • explain how the acid mantle protects the skin. • explain how soaps affect the skin pH. • know what conditions and diseases affect the skin surface pH. Target Audience: Dermatologists, Plastic Surgeons, Internists Commercial support: This activity is supported by an educational grant from CollaGenex Pharmaceuticals. I t’s well known that the skin is the first line of defense against all elements, such as microorganisms, wind and pollutants. And it’s the acid mantle, a fine film with a slightly acidic pH on the surface of the skin, which provides a protection for the skin. It plays a very important role as an integral part of the barrier function of the stratum corneum. Recent studies have demonstrated that increased enzyme activity of phospholipase A2 is related to the formation of the acid mantle in the stratum corneum.1,2 This combination makes the skin less permeable to water and other polar compounds. It also contributes to the low pH of the skin surface. Normal skin surface pH is between 4 and 6.5 in healthy people, though it varies among the different areas of the skin. Newborn infants do have a higher skin surface pH compared to adults, but this normalizes within 3 days.3 It’s important to protect the stratum corneum because if it’s damaged, skin surface pH has been shown to increase,4-5 creating susceptibility to bacterial skin infections or skin damage and disease. Providing Protection The acid mantle protects the skin from bacterial and fungal infections. The acid mantle contains lactic acid and various amino acids from sweat, free fatty acids from sebum, and amino acids and pyrrolidine carboxylic acid from the cornification process of skin. The acid mantle: • supports the formation and maturing of epidermal lipids and therefore the maintenance of the barrier function. • provides indirect protection against invasion by microorganisms. • provides direct protection against alkaline substances (alkali neutralizing-capacity). If the acid mantle becomes disrupted or damaged, or loses its acidity, the skin becomes more prone to damage and infection. Washing skin with soaps or detergents can cause the loss of acid mantle. Repetitive washing alters the stratum corneum and barrier functions, including skin pH. Once damaged, it can take up to 14 hours to restore, by which time, it’s most likely under assault again from another washing. Most people wash their hands about three times a day, on average. Single washings shift pH to the alkaline region, which can shift back to normal within a few hours. Other Factors that Affect pH There are many diseases that cause an increase in skin surface pH. (See "Skin and Systemic Diseases that Increase the Skin Surface pH.") Skin conditions that can cause this phenomenon include: • eczema • contact dermatitis • atopic dermatitis • dry skin. Acute eczema with erosion can cause skin surface pH to shift from normal to 7.3 to 7.4.5 This is a 1,000-fold increase in the pH shift as pH is measured in logarithmic function. The entire skin surface pH is increased on skin of people with atopic dermatitis.5 An increased skin pH contributes to Staphylococcus aureus colonization, which can play a role in the genesis of atopic dermatitis, discoid eczema, and infective dermatitis as a superantigen.5,6 Systemic diseases that can cause an increase in skin surface pH include: • diabetes • chronic renal failure • cerebrovascular disease (CVD).7-9 The explanation for the elevated pH in these diseases is not clear, but is possibly related to low levels of phospholipase and to autonomic dysfunction causing abnormal sweat secretion. An increase in skin surface pH encourages bacterial growth. Diabetic patients have an increase in skin surface pH in intertriginous areas, and it’s known that diabetic patients are more prone to Candidal infections, especially in intertriginous areas. Studies have shown that Candidal skin lesions are more pronounced on skin with higher pH values,10 possibly due to a pH dependence of the yeast’s virulence capacity and/or a modulation of the host defense capacity. C. albicans is dimorphic and an acidic pH favors the blastospore form while an increased pH favors the hyphael form. The hyphael form of Candida is the initial invader that grows best at pH >6.5, and diabetic patients have a decreased level of skin lactic acid.8 The use of skin occlusive products, such as dressings and diapers, are known to raise skin pH and are associated with skin infections caused by C. albicans. It’s common for patients with intertrigo to wash more often with harsh soaps, thinking that cleaner skin will help relieve their problem. However, harsh soaps with high pH only exacerbate the condition. Instead, the role of acidic soaps should be emphasized. Products to Use to Maintain pH Levels There are three main categories of cleansing agents: • soaps • synthetic detergents • lipid-free cleansing agents. It’s been shown that soaps make the skin more alkaline than synthetic detergents.11,12 The irritancy potential of cleansing agents is dependent on a number of factors, which include pH, and soaps are known to increase skin surface pH.12-14 Acidic cleansers are less irritating than neutral or alkaline ones, and people prone to dry skin are advised to use acidic cleansers. Agents with slightly acidic or neutral pH, nonionic surfactants, may be preferable for patients who are at increased risk for irritating skin reactions. Therefore, advise patients with skin conditions such as atopic dermatitis, acne vulgaris, rosacea, photoaging and sensitive skin, to choose a mild cleansing agent with a low pH — this is important in adjunctive care.12 The more neutral and alkaline soaps will make skin relatively more alkaline, which favors Propionibacterium growth. The number of Propionibacteria is significantly linked to skin pH,14 therefore it’s better to use soaps with a lower pH, especially for people prone to acne. Even minor differences in the pH of skin cleansing preparations can be important to the integrity of the skin surface. This should be taken into account when determining the optimal soap. With regard to Propionibacteria, studies have shown that the bacteria increase with the use of soaps and are decreased with the use of synthetic detergents.11 This factor may explain why synthetic detergents seem to be helpful in the treatment of acne, where Propionibacteria plays a major part.11 It’s especially important to avoid using soaps and cleansers with pH above 7.0 in babies because of the low pH of the tears, which is in the range of 6.5 to 7. Cleansers with a lower pH allow for the product to be much milder to the eyes; a higher priority for baby products. What’s Really on the Market Since the effectiveness of low pH soaps and cleansers has been well documented,12-14 one would think that companies producing home care products would try to market their products in this fashion. However, the market in the United States carries very few low-pH soaps and cleansers. Unless we, as dermatologists, educate our patients about the importance of low-pH cleansers and what’s available, they won’t know to look beyond the most common soaps on the market. (See "The pH of the Most Common Hand Soaps in the United States.") Most cleansers in the United States, with a few exceptions, are at a pH of 9.5 to 10.5. This pH is inherent to the formula, which is a sodium soap of fatty acids. The formulas that have a neutral pH are called "syndet." Chemically, they are not soaps, but a synthetic detergent in a bar form (thus their names). Some are called "combi-bars" (i.e. a combination of soap and synthetic detergents), whose pH is around 7.0 to 7.5. Interestingly, in Europe and Asia there is broad range of liquid washes, and even soaps, with a pH of 5.5, and the emphasis in the marketing there is in advertising a soap’s low pH. Low-pH moisturizers also are rarely marketed in the United States. These moisturizers, which help maintain the hydration and natural moisturizing factor of the stratum corneum are useful in maintaining the acid mantle. Because the acid mantle plays a part in preserving the skin barrier function, we believe there’s a need to address this part of the market as well.

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