title: Induction of a hardening phenomenon and quantitative changes of ceramides in stratum corneum.
abstract: BACKGROUND
  Hardening phenomenon of human skin after repeated exposure to the irritants is well-known, but the precise mechanism remains elusive.
  
  
  OBJECTIVE
  To modify the previous experimental model of hardening phenomenon by repeated applications of two different concentrations of sodium lauryl sulfate (SLS) solutions to Korean healthy volunteers and to investigate the quantitative changes of ceramides in stratum corneum before and after chronic repeated irritation.
  
  
  METHODS
  Eight hundred microliters of distilled water containing 0.1% and 2% SLS was applied for 10 minutes on the forearm of 41 healthy volunteers for 3 weeks. After an intervening 3-week rest, 24-hour patch tests with 1% SLS were conducted on previously irritated sites. Transepidermal water loss (TEWL), erythema index and quantity of ceramide were measured in the stratum corneum before and after irritation.
  
  
  RESULTS
  TEWL values on the sites preirritated with 2% SLS were lower than those with 0.1% SLS. Hardening phenomenon occurred in 24 volunteers at day 44. The changes in ceramide levels were not significantly higher in the hardened skin than in the non-hardened skin.
  
  
  CONCLUSIONS
  Repetitive stimulation with a higher concentration of SLS can more easily trigger skin hardening.
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Sook Young
authors.initials: SY
authors.lastname: Park
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Jin Hye
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Soo Ick
authors.initials: SI
authors.lastname: Cho
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Kyeong Il
authors.initials: KI
authors.lastname: Kim
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Cho
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Chun Wook
authors.initials: CW
authors.lastname: Park
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Cheol Heon
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Department of Dermatology, Hallym University Kangnam Sacred Heart Hospital, Seoul, Korea.
authors.forename: Hye One
authors.initials: HO
authors.lastname: Kim
keywords: Ceramides; Hardening phenomenon; Irritation contact dermatitis