title: Mapping the human face: biophysical properties.
abstract: BACKGROUND
  Facial skin exhibits unique biophysical properties that are distinct from skin belonging to other areas of the body. Small to large regional differences in biophysical properties between facial sites are observed. Technological advances in dermatological research allow a quantitative study of the biophysical qualities of the face and its relation to skin elsewhere. However, comprehensive studies examining inter-regional variations using each of the six standard biophysical parameters have been few. We summarize findings on the biophysical parameters used to explore the human face as well as regional differences in skin reactivity to chemical irritants.
  
  
  METHODS
  We performed a literature search using Pubmed, Embase, Science Citations Index, and the UCSF's dermatological library on biophysical parameters and skin physiology pertaining to the human face.
  
  
  RESULTS
  Distinct regional differences in transepidermal water loss (TEWL), capacitance, blood flow, sebum, pH, and temperature were demonstrated in facial skin. However, studies cannot be compared with each other because each uses different anatomical sites, skin conditions, and measurement techniques. Intraregional differences in TEWL, sebum, and temperatures were observed on the cheeks and appeared to follow characteristic distribution patterns. Higher blood flow levels and skin temperatures were generally observed in areas with dense networks of blood vessels such as the nose and perioral region. Areas such as the forehead, nose, and chin consistently showed higher sebum casual levels, but variability in sebum levels between sites was also observed. The susceptibility of the face to hexyl nicotinate, sodium lauryl sulfate, and benzoic acid differed depending on location and age.
  
  
  CONCLUSIONS
  Establishing a standardized biophysical profile of the human face will help to improve therapeutics, and further our understanding of differences in chemical reactivity and disease distribution. Future research necessitates standardization of the anatomical sites studied, sample size, and experimental protocols.
authors.affiliation: University of California, Irvine, CA, USA.
authors.forename: Chrystal V
authors.initials: CV
authors.lastname: Wa
authors.forename: Howard I
authors.initials: HI
authors.lastname: Maibach
mesh_terms: D001703:Biophysics; D025802:Electric Capacitance; D005145:Face / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017078:Laser-Doppler Flowmetry; D012629:Sebum / Q000378:metabolism*; D012867:Skin / Q000098:blood supply / Q000378:metabolism*; D012869:Skin Absorption / Q000502:physiology; D023422:Skin Irritancy Tests; D012881:Skin Temperature / Q000502:physiology; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water