title: Tachyphylaxis to histamine-induced wheal suppression by topical 0.05% clobetasol propionate in normal versus croton oil-induced dermatitic skin.
abstract: BACKGROUND
  Patients often tell about reduced effectiveness of topical steroids on repeated use. Tachyphylaxis to these agents has been demonstrated in humans for vasoconstriction and histamine-induced wheal suppression in normal skin, but not in diseased skin. Relevance of these data to diseased skin is not clear. Further, the clinical impression does not appear to match tachyphylaxis shown in normal skin with regard to the time course.
  
  
  OBJECTIVE
  To examine whether tachyphylaxis to histamine-induced wheal suppression by a topical steroid occurs in dermatitic skin and to determine its time course vis-à-vis normal skin.
  
  
  METHODS
  Pharmacodynamic response to 0.05% clobetasol propionate applied daily under occlusion was measured by histamine-induced wheal suppression assay in 10 individuals. This test was performed on a steroid-treated normal site, on a steroid-treated site where dermatitis was induced by occlusive application of 40% croton oil, and on a vehicle-treated site in each individual at different intervals up to 14 days.
  
  
  RESULTS
  Suppression of wheal volume started from second day in steroid-treated sites. There was significant difference in the wheal volume in steroid treated normal vs. dermatitic sites from day 2 to day 10. Maximum wheal suppression occurred earlier in dermatitic skin (day 4 vs. day 6). After this, the volume of wheal started increasing and became equal to control (complete tolerance) on 12th day in dermatitic skin and on 14th day in normal skin.
  
  
  CONCLUSIONS
  Time courses of tachyphylaxis to the action of 0.05% clobetasol propionate were significantly different in normal skin and dermatitic skin. Complete tolerance occurred earlier in dermatitic skin compared to normal skin.
authors.affiliation: Department of Dermatology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India.
authors.forename: S
authors.initials: S
authors.lastname: Singh
authors.forename: A
authors.initials: A
authors.lastname: Gupta
authors.forename: S S
authors.initials: SS
authors.lastname: Pandey
authors.forename: G
authors.initials: G
authors.lastname: Singh
mesh_terms: D000287:Administration, Topical; D000328:Adult; D000893:Anti-Inflammatory Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002990:Clobetasol / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D003436:Croton Oil / Q000009:adverse effects*; D003877:Dermatitis, Contact / Q000503:physiopathology*; D005938:Glucocorticoids; D006632:Histamine / Q000009:adverse effects*; D006801:Humans; D007509:Irritants / Q000009:adverse effects*; D008297:Male; D012867:Skin / Q000187:drug effects*; D013618:Tachyphylaxis / Q000502:physiology*; D014581:Urticaria / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*
chemical_list: D000893:Anti-Inflammatory Agents; D005938:Glucocorticoids; D007509:Irritants; D003436:Croton Oil; D006632:Histamine; D002990:Clobetasol