Each biological system possesses a widely unrecognized buffer system to maintain acid-base balance to a specific pH. The skin pH is crucial for physiological skin function. In aged or diseased skin, pH increase is observed and may negatively affect skin health. Skin care products with a pH that is slightly more acidic than the average normal skin pH and have an adequate buffering capacity, are considered beneficial for the skin. However, the buffer capacity of these products also plays an important role. In the present study, a possible normalization or acidification of skin surface pH and influence on skin hydration and skin barrier function was assessed via application of buffered skin care products that are formulated with pH ≤ 4.5. 48 subjects aged above 50 were treated with three different skin care products (Vitamin C Spheres, Collagen Spray, and Collagen Mask) and skin surface pH, skin hydration and barrier integrity were assessed before treatment start and after 4 weeks. The results show that after 4-week treatment with Vitamin C, the skin pH is acidified. Treatment with Collagen Spray and Collagen Mask showed maintenance of a physiological skin pH. Subgroup analysis of subjects that had a higher than average skin pH at study start demonstrated that all three tested skin care products were able to acidify the skin surface. In addition, skin hydration was also increased for two of the three tested products, whereas skin barrier is not significantly changed. This demonstrates that buffered skin care products formulated to a pH ≤ 4.5 are able to acidify and maintain physiological skin pH and may contribute to a physiological skin function.
References
[1]
Proksch, E. (2018) Buffering Capacity. Current Problems in Dermatology, 54, 11-18. https://doi.org/10.1159/000489513
Ali, S.M. and Yosipovitch, G. (2013) Skin pH: From Basic Science to Basic Skin Care. Acta Dermato-Venereologica, 93, 261-267. https://doi.org/10.2340/00015555-1531
[4]
Schmid-Wendtner, M.H. and Korting, H.C. (2006) The pH of the Skin Surface and Its Impact on the Barrier Function. Skin Pharmacology and Physiology, 19, 296-302. https://doi.org/10.1159/000094670
[5]
Schreml, S., Zeller, V., Meier, R.J., Korting, H.C., Behm, B., Landthaler, M., et al. (2012) Impact of Age and Body Site on Adult Female Skin Surface pH. Dermatology, 224, 66-71. https://doi.org/10.1159/000337029
[6]
Segger, D., Aßmus, U., Brock, M., Erasmy, J., Finkel, P., Fitzner, A., et al. (2008) Multicenter Study on Measurement of the Natural pH of the Skin Surface. International Journal of Cosmetic Science, 30, 75. https://doi.org/10.1111/j.1468-2494.2007.00403_1.x
[7]
Levin, J. and Maibach, H. (2008) Human Skin Buffering Capacity: An Overview. Skin Research and Technology, 14, 121-126. https://doi.org/10.1111/j.1600-0846.2007.00271.x
[8]
Choi, E.H. (2018) Gender, Age, and Ethnicity as Factors That Can Influence Skin pH. Current Problems in Dermatology, 54, 48-53. https://doi.org/10.1159/000489517
[9]
Wohlrab, J. and Gebert, A. (2018) pH and Buffer Capacity of Topical Formulations. Current Problems in Dermatology, 54, 123-131. https://doi.org/10.1159/000489526
[10]
Lambers, H., Piessens, S., Bloem, A., Pronk, H. and Finkel, P. (2006) Natural Skin Surface pH Is on Average below 5, Which Is Beneficial for Its Resident Flora. International Journal of Cosmetic Science, 28, 359-370. https://doi.org/10.1111/j.1467-2494.2006.00344.x
[11]
Noble, W.C. (1993) Staphylococci on the Skin. In: The Skin Microflora and Microbial Skin Disease, Cambridge University Press, Cambridge, 135-152. https://doi.org/10.1017/CBO9780511527012.007
[12]
Holland, K.T. and Bojar, R.A. (2002) Cosmetics: What Is Their Influence on the Skin Microflora? American Journal of Clinical Dermatology, 3, 445-449. https://doi.org/10.2165/00128071-200203070-00001
[13]
Farage, M.A., Hood, W., Berardesca, E. and Maibach, H. (2018) Intrinsic and Extrinsic Factors Affecting Skin Surface pH. Current Problems in Dermatology, 54, 33-47. https://doi.org/10.1159/000489516
[14]
Danby, S.G. and Cork, M.J. (2018) pH in Atopic Dermatitis. Current Problems in Dermatology, 54, 95-107. https://doi.org/10.1159/000489523
[15]
Schurer, N. (2018) pH and Acne. Current Problems in Dermatology, 54, 115-122. https://doi.org/10.1159/000489525
[16]
Proksch, E., Soeberdt, M., Neumann, C., Reich, H. and Abels, C. (2018) 670 Topically Applied Buffers of Different pH and Composition Influence Skin pH, Barrier Repair, Epidermal Differentiation, and Inflammation. Journal of Investigative Dermatology, 138, S114. https://doi.org/10.1016/j.jid.2018.03.679
[17]
Oman, S.V. and Ritonja, A. (1984) Die Pufferkapazität kosmetischer und pharmazeutischer Emulsionen. Parfümerie und Kosmetik, 65, 186-189.
[18]
Hyde, R., Puy, R.J., Raub, W.F. and Forster, R.E. (1968) Rate of Disappearance of Labeled Carbon Dioxide from the Lungs of Humans during Breath Holding: A Method for Studying the Dynamics of Pulmonary CO2 Exchange. Journal of Clinical Investigation, 47, 1535-1552. https://doi.org/10.1172/JCI105846
[19]
Schreml, S., Meier, R.J., Weiss, K.T., Cattani, J., Flittner, D., Gehmert, S., et al. (2012) A Sprayable Luminescent pH Sensor and Its Use for Wound Imaging in Vivo. Experimental Dermatology, 21, 951-953. https://doi.org/10.1111/exd.12042
[20]
Elias, P.M. and Wakefield, J.S. (2014) Mechanisms of Abnormal Lamellar Body Secretion and the Dysfunctional Skin Barrier in Patients with Atopic Dermatitis. The Journal of Allergy and Clinical Immunology, 134, 781-791e1. https://doi.org/10.1016/j.jaci.2014.05.048
[21]
Pankratov, V.G. (1970) Study of the pH and rH2 of the Skin Surface in Patients with Psoriasis and Eczema. Vestnik Dermatologii i Venerologii, 44, 20-25.
[22]
Ohman, H. and Vahlquist, A. (1998) The pH Gradient over the Stratum Corneum Differs in X-Linked Recessive and Autosomal Dominant Ichthyosis: A Clue to the Molecular Origin of the “Acid Skin Mantle”? Journal of Investigative Dermatology, 111, 674-677. https://doi.org/10.1046/j.1523-1747.1998.00356.x
[23]
Proksch, E., Jensen, J.M. and Elias, P.M. (2003) Skin Lipids and Epidermal Differentiation in Atopic Dermatitis. Clinics in Dermatology, 21, 134-144. https://doi.org/10.1016/S0738-081X(02)00370-X
[24]
Shi, V.Y., Tran, K. and Lio, P.A. (2012) A Comparison of Physicochemical Properties of a Selection of Modern Moisturizers: Hydrophilic Index and pH. Journal of Drugs in Dermatology, 11, 633-636.
[25]
Gunathilake, R., Schurer, N.Y., Shoo, B.A., Celli, A., Hachem, J.P., Crumrine, D., et al. (2009) pH-Regulated Mechanisms Account for Pigment-Type Differences in Epidermal Barrier Function. Journal of Investigative Dermatology, 129, 1719-1729. https://doi.org/10.1038/jid.2008.442
[26]
Surber, C., Humbert, P., Abels, C. and Maibach, H. (2018) The Acid Mantle: A Myth or an Essential Part of Skin Health? Current Problems in Dermatology, 54, 1-10. https://doi.org/10.1159/000489512
[27]
Blaak, J., Wohlfart, R. and Schürer, N.Y. (2011) Treatment of Aged Skin with a pH 4 Skin Care Product Normalizes Increased Skin Surface pH and Improves Barrier Function: Results of a Pilot Study. Journal of Cosmetics, Dermatological Sciences and Applications, 1, 50-58. https://doi.org/10.4236/jcdsa.2011.13009
[28]
Kilic, A., Masur, C., Reich, H., Knie, U., Dahnhardt, D., Dahnhardt-Pfeiffer, S., et al. (2019) Skin Acidification with a Water-in-Oil Emulsion (pH 4) Restores Disrupted Epidermal Barrier and Improves Structure of Lipid Lamellae in the Elderly. The Journal of Dermatology, 46, 457-465. https://doi.org/10.1111/1346-8138.14891
[29]
Man, M.Q., Xin, S.J., Song, S.P., Cho, S.Y., Zhang, X.J., Tu, C.X., et al. (2009) Variation of Skin Surface pH, Sebum Content and Stratum Corneum Hydration with Age and Gender in a Large Chinese Population. Skin Pharmacology and Physiology, 22, 190-199. https://doi.org/10.1159/000231524
[30]
Luebberding, S., Krueger, N. and Kerscher, M. (2013) Age-Related Changes in Skin Barrier Function—Quantitative Evaluation of 150 Female Subjects. International Journal of Cosmetic Science, 35, 183-190. https://doi.org/10.1111/ics.12024
[31]
Luebberding, S., Krueger, N. and Kerscher, M. (2014) Age-Related Changes in Male Skin: Quantitative Evaluation of One Hundred and Fifty Male Subjects. Skin Pharmacology and Physiology, 27, 9-17. https://doi.org/10.1159/000351349
[32]
Zlotogorski, A. (1987) Distribution of Skin Surface pH on the Forehead and Cheek of Adults. Archives of Dermatological Research, 279, 398-401. https://doi.org/10.1007/BF00412626
[33]
Abels, C. and Angelova-Fischer, I. (2018) Skin Care Products: Age-Appropriate Cosmetics. Current Problems in Dermatology, 54, 173-182. https://doi.org/10.1159/000489531
[34]
Rippke, F., Berardesca, E. and Weber, T.M. (2018) pH and Microbial Infections. Current Problems in Dermatology, 54, 87-94. https://doi.org/10.1159/000489522
[35]
Sato, N., Kitahara, T. and Fujimura, T. (2014) Age-Related Changes of Stratum Corneum Functions of Skin on the Trunk and the Limbs. Skin Pharmacology and Physiology, 27, 181. https://doi.org/10.1159/000353912
[36]
Ghadially, R., Brown, B.E., Sequeira-Martin, S.M., Feingold, K.R. and Elias, P.M. (1995) The Aged Epidermal Permeability Barrier. Structural, Functional, and Lipid Biochemical Abnormalities in Humans and a Senescent Murine Model. Journal of Clinical Investigation, 95, 2281-2290. https://doi.org/10.1172/JCI117919
[37]
Darlenski, R., Kazandjieva, J., Fluhr, J.W., Maurer, M. and Tsankov, N. (2014) Lactic Acid Sting Test Does Not Differentiate between Facial and Generalized Skin Functional Impairment in Sensitive Skin in Atopic Dermatitis and Rosacea. Journal of Dermatological Science, 76, 151-153. https://doi.org/10.1016/j.jdermsci.2014.08.014
[38]
Sahlin, A., Edlund, F. and Loden, M. (2007) A Double-Blind and Controlled Study on the Influence of the Vehicle on the Skin Susceptibility to Stinging from Lactic Acid. International Journal of Cosmetic Science, 29, 385-390. https://doi.org/10.1111/j.1468-2494.2007.00396.x
[39]
Stiller, M.J., et al. (1996) Topical 8% Glycolic Acid and 8% L-Lactic Acid Creams for the Treatment of Photodamaged Skin. A Double-Blind Vehicle-Controlled Clinical Trial. Archives of Dermatology, 132, 631-636. https://doi.org/10.1001/archderm.132.6.631
[40]
Sourla, D., Dallas, P., Rekkas, D. and Choulis, N. (2003) Optimization of in Vitro Skin Permeation by Lactic Acid from Gel Formulations. Journal of Cosmetic Science, 54, 421-426.
