The Impact of 10% α-Hydroxy Acid Emulsion on Skin pH

Abstract

Background/Aims: The effects of a 10% α-hydroxy acid (AHA) oil/water (O/W) emulsion on the pH of human skin surface (pH_ss) and stratum corneum (SC; pH_sc) were evaluated in vivo. Methods: The AHA O/W emulsion was applied to an area on the volar forearm of male volunteers (n = 12), and then wiped off after 10 min. Prior to application and over the following 3 h, the pH_ss was measured. We used glass electrode measurements and time domain dual lifetime referencing (tdDLR) with luminescent sensor foils. In another experiment (n = 5), the impact of the AHA O/W emulsion on the pH_sc gradient was measured by tape stripping of the SC of the volar forearm after application of the AHA O/W emulsion. Results: Compared with pH_ss values prior to treatment [5.2 ± 1.7 (tdDLR) or 4.8 ± 0.5 (electrode)], the pH_ss was significantly reduced 10 min after application [4.0 ± 0.3 (tdDLR) or 4.1 ± 0.1 (electrode)] and the pH_ss remained significantly reduced over the measurement period of 3 h [after 3 h: 4.4 ± 0.2 (tdDLR) or 4.5 ± 0.3 (electrode)]. The AHA O/W emulsion significantly reduced the pH_sc even down to deep layers of the SC. Conclusion: After a 10-min application time, the 10% AHA O/W emulsion reduces the pH_ss (for at least 3 h) and pH_sc in deep layers of the SC.

Standardized extract of wild apple fruit in alkyl‐polyglucoside‐based cosmetic cream – estimation of stability, safety, antioxidant activity and efficiency

“…Lactic acid could be synthesized by reduction of pyruvic acid or transformation of malic acid. Detected concentrations of succinic, malic, tartaric and lactic acids in investigated samples EW and EM might indicate that these acids might be responsible for the efficiency of cosmetic cream EM .…”

Impact of a Glycolic Acid-Containing pH 4 Water-in-Oil Emulsion on Skin pH

“…In contrast to previous studies investigating a pH 4 O/W emulsion [15], the effect on pH SS of a pH 4 W/O emulsion was investigated regarding the acidifying properties. The two different emulsion types (W/O and O/W) exhibit different properties and thus differ with respect to influencing the pH SS .…”

“…glycolic acid)-containing O/W formulations are widely used in cosmetics and dermatology [14]. In a previous study, we showed that the application of a 10% glycolic acid-containing O/W emulsion with pH 4 reduced not only the pH SS but also led to a significant decrease of the pH in deeper layers of the SC (pH SC ), very likely even affecting the stratum granulosum [15]. …”

Impact of a pH 5 Oil-in-Water Emulsion on Skin Surface pH

“…A significant reduction of the baseline pH ss could potentially be achieved by a longer application period or an O/W emulsion with a more acidic pH, like in previous studies [22,23]. …”

“…Several target groups that may profit from these products in particular have been defined in other studies (e.g., elderly, patients with atopic dermatitis, diabetics) [14,15,19,20,21,22]. Prior research of our study group examined the effect of a pH 4 water-in-oil (W/O) emulsion as well as a 10% α-hydroxy acid O/W emulsion on pH ss and pH sc in healthy subjects and diabetics [19,23]. …”