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Influence of the quantity of sunscreen applied on the ability to protect against ultraviolet‐induced polymorphous light eruption
Author(s) -
Bissonnette Robert,
Nigen Simon,
Bolduc Chantal
Publication year - 2012
Publication title -
photodermatology, photoimmunology and photomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.736
H-Index - 60
eISSN - 1600-0781
pISSN - 0905-4383
DOI - 10.1111/j.1600-0781.2012.00678.x
Subject(s) - ultraviolet , ultraviolet a , ultraviolet light , ultraviolet radiation , environmental science , chemistry , dermatology , materials science , medicine , optoelectronics , photochemistry , radiochemistry
Summary Background/Purpose 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). Conclusion 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 .