Influence of skin cleansing preparation acidity on skin surface properties

Abstract

Synopsis Two long-term trials were conducted each over eight weeks to compare the effect of the regular application of skin cleansing preparations of pH 5.5 and pH 8.5 and pH 5.5 and pH 7.0 respectively on the surface pH, roughness and transepidermal water loss (TEWL) of normal human forehead and forearm skin. Both trials were based on a cross-over design: five healthy volunteers started with a pH 5.5 preparation and switched to the other after four weeks, five additional volunteers used the preparations in the opposite order. While the skin surface pH was markedly lower in those individuals using the pH 5.5 preparation at each examination, as compared to those using the pH 8.5 or pH 7.0 preparation, no such difference could be established with respect to skin roughness and TEWL. Hence the skin irritancy of a cleansing preparation does not seem to be linked to its pH within the pH ranges tested.

Application of Topical Acids Improves Atopic Dermatitis in Murine Model by Enhancement of Skin Barrier Functions Regardless of the Origin of Acids

“…Therefore this implies that in the setting of low pH, the NaOH does not act as an irritant. This corresponds with the report by Korting et al31, which showed no difference in skin roughness and TEWL that represent skin irritation, when the same cleansing preparations except for the pH itself based on a different amount of NaOH included are used. In Fig.…”

The Concept of the Acid Mantle of the Skin: Its Relevance for the Choice of Skin Cleansers

“…The validity of this hypothesis has been corroborated by clinical investigations. In 1989, Antoine et al 1241 con cluded from investigations based on the assessment of cuta neous blood flow values that the 'pH cannot be considered as a major contributive factor of irritancy', at least with respect to the well-known model irritant sodium lauryl sul fate applied under occlusion over 48 h. This is in accord ance with our findings comparing synthetic cleansers, as described with pH 5.5, 7.0 and 8.5, a judgment based on the parameters transepidermal water loss and skin roughness expressed as mean peak-to-valley height or RZUIN values [25]. Using infrared spectroscopy and corneometry, i.e., skin capacitance measurements, Gehring et al [26] even described 'a greater dchydrative effect at alkaline pH (7.5) than at neutral or acidic pH (4.5)'.…”

Treatment of Surfactant-Damaged Skin in Humans with Creams of Different pH Values

“…Also skin protectants based upon zinc oxide have an alkaline pH. In addition, the clinical relevance of marketing of acidic cleansers as gentle to the skin due to their low pH have been questioned [31,32]. The reported difference in irritating capacity between cleansers with various pH values [33] may depend on the combination of surfactants and their inherent irritating capacity, rather than the pH of the products [27].…”