title: The impact of 10% α-hydroxy acid emulsion on skin pH.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Dermatology, University Hospital Regensburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schreml
authors.forename: R J
authors.initials: RJ
authors.lastname: Meier
authors.forename: M G
authors.initials: MG
authors.lastname: Albert
authors.forename: U
authors.initials: U
authors.lastname: Seidl
authors.forename: V
authors.initials: V
authors.lastname: Zeller
authors.forename: B
authors.initials: B
authors.lastname: Behm
authors.forename: M
authors.initials: M
authors.lastname: Landthaler
authors.forename: C
authors.initials: C
authors.lastname: Abels
authors.forename: P
authors.initials: P
authors.lastname: Babilas
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D004566:Electrodes; D004655:Emulsions / Q000493:pharmacokinetics; D005542:Forearm; D006016:Glycolates / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007641:Keratolytic Agents / Q000494:pharmacology*; D008163:Luminescent Measurements; D008297:Male; D012867:Skin; D055815:Young Adult
chemical_list: D004655:Emulsions; D006016:Glycolates; D007641:Keratolytic Agents; C031149:glycolic acid