title: Daytime Changes of Skin Biophysical Characteristics: A Study of Hydration, Transepidermal Water Loss, pH, Sebum, Elasticity, Erythema, and Color Index on Middle Eastern Skin.
abstract: BACKGROUND
  The exposure of skin to ultraviolet radiation and temperature differs significantly during the day. It is reasonable that biophysical parameters of human skin have periodic daily fluctuation. The objective of this study was to study the fluctuations of various biophysical characteristics of Middle Eastern skin in standardized experimental conditions.
  
  
  METHODS
  Seven biophysical parameters of skin including stratum corneum hydration, transepidermal water loss, pH, sebum, elasticity, skin color, and erythema index were measured at three time points (8 a.m., 12 p.m. and 4 p.m.) on the forearm of 12 healthy participants (mean age of 28.4 years) without any ongoing skin disease using the CK MPA 580 device in standard temperature and humidity conditions.
  
  
  RESULTS
  A significant difference was observed between means of skin color index at 8 a.m. (175.42 ± 13.92) and 4 p.m. (164.44 ± 13.72,P= 0.025), between the pH at 8 a.m. (5.72 ± 0.48) and 4 p.m. (5.33 ± 0.55,P= 0.001) and pH at 12 p.m. (5.60 ± 0.48) and 4 p.m. (5.33 ± 0.55,P= 0.001). Other comparisons between the means of these parameters at different time points resulted in nonsignificantPvalues.
  
  
  CONCLUSIONS
  There are daytime changes in skin color index and pH. Skin color index might be higher and cutaneous pH more basic in the early morning compared to later of the day.
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Firooz
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hamed
authors.initials: H
authors.lastname: Zartab
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Bardia
authors.initials: B
authors.lastname: Sadr
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Leili Naraghi
authors.initials: LN
authors.lastname: Bagherpour
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Aidin
authors.initials: A
authors.lastname: Masoudi
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Ferial
authors.initials: F
authors.lastname: Fanian
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Yahya
authors.initials: Y
authors.lastname: Dowlati
authors.affiliation: Department of Dermatology, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Amir Hooshang
authors.initials: AH
authors.lastname: Ehsani
authors.affiliation: Center for Research and Training in Skin Diseases and Leprosy, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Aniseh
authors.initials: A
authors.lastname: Samadi
keywords: Color; pH; skin barrier; skin structure; statistics; transepidermal water loss