Do Broad Spectrum Sunscreens Allow Ultraviolet-Induced Photodamage in the Absence of Erythema?

Abstract

Broad spectrum, high sun protection factor (SPF) sunscreens have been shown, unequivocally, to prevent sunburn as long as the UV dose does not exceed the protective factor of the sunscreen.1, 2 Although the acute effects of sunlight can be readily studied in humans, assessment of sunscreen efficacy against the damage caused by chronic irradiation requires an animal model. The hairless mouse has been and continues to be a useful model for these purposes.3 High SPF products have been shown to prevent UVB-induced carcinogenesis in these mice.4,5 The model has been established as a relevant one for the study of photoaging 3,6,7 because the dermal connective tissue changes closely resemble those found in human sun worshippers.8 Sunscreen prevention of UVB-induced photoaging has been repeatedly demonstrated.6,7,9 Dermal damage induced by long-term UVA exposure has also been prevented by sunscreens containing UVA-absorbing molecules.10, 11 Similarly, sunscreen protection against chronic exposure to solar simulating radiation (UVB plus UVA) has been shown.12 In summary, experimental studies with the hairless mouse have reported that sunscreens provide virtually complete protection against photodamage resulting from chronic exposure to UV radiation.