98 TESTING Alkaline cleansers may additionally
increase the negative electrical net charge of the hair fibre surface and the friction between the hair fibres, causing frizz, hair breakage and enhancing hair entangling.29
Thus, cosmetic
products being developed – cleansers, hair care and skincare - have to overcome extraordinary challenges. Not only their effectiveness but also their impact on the skin pH value should be checked and supported by skin testing using classical bioengineering methods.
Easy and quick pH measurement Skin and scalp pH can be easily measured, using special electrodes with a flat measurement head that touch the skin over an area of approximately 10mm in diameter. The values are displayed within one or two seconds. For measurement of the pH gradient in different layers of the stratum corneum, sequential skin stripping by adhesive tapes such as Corneofix or Desquame is practised.18 Besides the pH development, it is also
important to monitor other changes occurring at the skin surface. Especially the measurement of hydration together with the assessment of sebum will show if and how a product affects or improves the skin condition. Additional information on the product compatibility and its irritating potential can be retrieved from measuring further parameters such as the barrier quality by the determination of TEWL (transepidermal water loss) or skin redness. The combination of these different
measurements will complete the picture, contributing to a detailed overview of the exact state of the skin, its strength or weaknesses and the effect of applied products.
References 1. Schade H, Marchionini A. Der Säuremantel der Haut (nach Gaskettenmessungen). Klinische Wochenschrift. 1928
2. Fluhr JW, Darlenski R. Skin Surface pH in Newborns: Origin and Consequences. In: Surber – Abels -Maibach (eds.): pH of the Skin: Issues and Challenges. Curr. Probl.
PC Dermatol. Basel, Karger. 2018; 54: 26-32
3. Enzmann C-C. Physiologie der Neugeborenen- und Säuglingshaut in den ersten drei Lebensmonaten. Dissertation. University Medical Centre Hamburg- Eppendorf. 2022
4. Yosipovitch G, Maayan-Metzger A, Merlob P. Skin barrier properties in different body areas in neonates. Pediatrics. 2000; 106: 105-108
5. Schreml S, Kemper M, Abels C. Skin pH in the Elderly and Appropriate Skin Care. EMJ Dermatol. 2014; 2: 86-94
6. Man MW, Xin SJ, Song SP, Cho SY, Zhang XJ, Tu CX, Feingold KR, Elias PM. Variation of Skin Surface pH, Sebum Content and Stratum Corneum Hydration with Age and Gender in a Large Chinese Population. Skin Pharmacol. Physiol. 2009 Sep; 22(4): 190–199
PERSONAL CARE April; 2023
www.personalcaremagazine.com
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