title: Influence of the quantity of sunscreen applied on the ability to protect against ultraviolet-induced polymorphous light eruption.
abstract: OBJECTIVE
  Despite the fact that most people apply less sunscreen than the 2 mg/cm(2)  required to measure sun protection factor (SPF), there is a lack of clinical data on the protection afforded from lower applied quantities. The aim of this study was to compare the ability of sunscreens to protect against UV-induced polymorphous light eruption (PLE) when applied at 2 mg/cm(2)  and 1 mg/cm(2) .
  
  
  METHODS
  Two SPF 45 sunscreens (one with a high level and one with a low level of UVA protection) were applied at 2 mg/cm(2)  and 1 mg/cm(2)  to four randomized 6 × 6 cm areas on the upper thorax of 15 female patients with a typical history of PLE. The areas were exposed daily to increasing UVA-UVB radiation until a PLE reaction was detected or a maximum of five consecutive days.
  
  
  RESULTS
  The proportion of patients who developed a PLE reaction with the high UVA-protection sunscreen was significantly lower (0%) than with the low UVA-protection sunscreen (73%) when both sunscreens were applied at 2 mg/cm(2)  (P = 0.004). At 1 mg/cm(2) , 33% and 80% of patients presented a PLE reaction with the high and low UVA-protection sunscreen, respectively (P = 0.064).
  
  
  CONCLUSIONS
  A high SPF and high UVA-protection broad spectrum sunscreen was able to protect the majority of patients from the development of UV-induced PLE reaction even at 1 mg/cm(2) .
authors.affiliation: Innovaderm Research Inc., Montreal, QC, Canada. rbissonnette@innovaderm.ca
authors.forename: Robert
authors.initials: R
authors.lastname: Bissonnette
authors.forename: Simon
authors.initials: S
authors.lastname: Nigen
authors.forename: Chantal
authors.initials: C
authors.lastname: Bolduc
mesh_terms: D000287:Administration, Topical; D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008875:Middle Aged; D012871:Skin Diseases / Q000517:prevention & control*; D013473:Sunscreening Agents / Q000008:administration & dosage*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D013473:Sunscreening Agents