title: Durability of the sun protection factor provided by dihydroxyacetone.
abstract: OBJECTIVE
  The sunless tanning agent dihydroxyacetone (DHA) is known to protect against longwave ultraviolet radiation (UVA) and visible light. Recently, our laboratory has shown that DHA in addition offers a modest sun protection factor (SPF) in humans. We conducted this study in order to investigate the durability of the SPF provided by DHA.
  
  
  METHODS
  Ten healthy volunteers were treated with 20% DHA cream twice in three areas on the volar forearm. One, 5 and 7 days after the second application the participants were phototested with simulated sunlight in each area. Blue reflectance was used to measure the skin coloration by DHA in the test sites.
  
  
  RESULTS
  DHA generated a significant SPF of 3.0 at day 1, 2.0 at day 5 and 1.7 at day 7 (P<0.0001). The SPF was positively correlated to the change in blue reflectance (r=0.39, P=0.034). The loss of SPF unit/day was not significantly different between the subjects (P<0.122). However, the intercepts were significantly different (P<0.0001) indicating differences in the initial SPF obtained among the subjects.
  
  
  CONCLUSIONS
  The SPF of DHA decreases with the same loss of SPF unit/day between humans and the durability of the SPF thus depends on the initial SPF provided.
authors.affiliation: Department of Dermatology, Bispebjerg Hospital, Bispebjerg Bakke, University of Copenhagen, 23 DK-2400 Copenhagen NV, Denmark. Fie_Faurschou@hotmail.com
authors.forename: A
authors.initials: A
authors.lastname: Faurschou
authors.forename: H C
authors.initials: HC
authors.lastname: Wulf
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D004098:Dihydroxyacetone / Q000008:administration & dosage / Q000627:therapeutic use*; D004643:Emollients; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012880:Skin Pigmentation / Q000528:radiation effects; D013473:Sunscreening Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D004643:Emollients; D013473:Sunscreening Agents; D004098:Dihydroxyacetone