title: Relationship between skin parameters (darkness or thickness) and photoreaction of Chinese Han skin.
abstract: BACKGROUND
  Skin pigmentation and the stratum corneum are the two primary natural factors that protect against UV damage. Although several classification systems exist to quantify the ability of the skin to protect itself from damaging UV radiation, few reports have assessed skin parameters and photoreaction in persons of Han Chinese descent.
  
  
  OBJECTIVE
  To understand the relationship between skin darkness, skin thickness, and photoreaction in Chinese Han subjects.
  
  
  METHODS
  Thirty-one subjects were exposed to UVA and UVB. Minimal persistent pigment darkening dose (MPPD) and minimal erythema dose (MED) were obtained. Before the UV irradiation, the test sites were measured by the Mexameter MX 16, Chromameter CR400, and Skin B-ultrasonic to determine skin color and thickness>. Using the ratio of J(MPPD)/J(MED), we classified the subjects into four energy skin phototypes (ESPTs) and the skin parameters for each of these groups were analyzed.
  
  
  RESULTS
  Skin color and skin thickness were significantly different among the ESPTs. There was also a significant positive correlation between skin group and the skin color and thickness parameters (b*, melanin index [MI], thickness). As the ESPTs increased from ESPT A to ESPT D, the mean dose to achieve MED increased, while the MPPD decreased.
  
  
  CONCLUSIONS
  As the ESPTs increased from type A to type D, there was a proclivity to tan rather than burn. Similarly, the skin became darker and thicker as the phototype increased from A to D.
authors.affiliation: Dermatological Department, Third affiliated hospital of Xuzhou Medical College, Xuzhou, China.
authors.forename: Mi-Na
authors.initials: MN
authors.lastname: Xia
authors.forename: Xue-Min
authors.initials: XM
authors.lastname: Wang
authors.forename: Yan-Qun
authors.initials: YQ
authors.lastname: Liu
authors.forename: Chao
authors.initials: C
authors.lastname: Yuan
authors.forename: Ying
authors.initials: Y
authors.lastname: Zou
authors.forename: Guo-Biao
authors.initials: GB
authors.lastname: Fan
mesh_terms: D000328:Adult; D044466:Asian People; D004890:Erythema / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012867:Skin / Q000033:anatomy & histology / Q000503:physiopathology / Q000528:radiation effects*; D012880:Skin Pigmentation / Q000528:radiation effects*; D014466:Ultraviolet Rays