title: Suppression of UV-induced erythema by topical treatment with melatonin (N-acetyl-5-methoxytryptamine). Influence of the application time point.
abstract: BACKGROUND
  In a previous study, we reported a significant and dose-dependent suppression of UV-induced erythema in human skin by a topically applied melatonin preparation.
  
  
  OBJECTIVE
  The present double-blind randomized study was designed to examine the influence of the application time point of topical melatonin on this antierythema effect.
  
  
  METHODS
  Defined small areas on the lower back of 20 volunteers were treated with 0.6 mg/cm2 melatonin dissolved in a nanocolloid gel carrier either 15 min before or 1, 30 or 240 min after UV irradiation with twice the individual minimal erythema dose delivered by a Multiport Solar UV Simulator (UVA and UVB). The erythemata induced were evaluated by visual scoring and chromametry 24 h after irradiation.
  
  
  RESULTS
  Treatment of the skin with melatonin 15 min before UV irradiation proved to almost completely suppress the development of an UV-induced erythema. In contrast, no significant protective effects of melatonin were observed when it was applied after UV irradiation.
  
  
  CONCLUSIONS
  Topically applied melatonin has a clear-cut protective effect against UV-induced erythema. Free radical scavenging of UV-generated hydroxyl radicals and interference with the arachidonic acid metabolism are possible mechanisms of the melatonin action.
authors.affiliation: Department of Dermatology, University of Zurich, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Bangha
authors.forename: P
authors.initials: P
authors.lastname: Elsner
authors.forename: G S
authors.initials: GS
authors.lastname: Kistler
mesh_terms: D000287:Administration, Topical; D000328:Adult; D004311:Double-Blind Method; D004890:Erythema / Q000209:etiology / Q000517:prevention & control*; D005260:Female; D016166:Free Radical Scavengers / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008550:Melatonin / Q000008:administration & dosage*; D012867:Skin / Q000528:radiation effects; D013471:Sunburn / Q000517:prevention & control; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D016166:Free Radical Scavengers; D008550:Melatonin