The importance of sun protection is known in today’s society better than it was in earlier decades. Specifically, the importance of protecting skin from both UVB radiation (290–320 nm), since it can cause severe sunburn damage and cancer, and UVA radiation (320–400 nm), which penetrates deeper into skin and produces reactive oxygen species (ROS) that can cause DNA, cell and tissue damage, is well-known. UVA is also noted to induce immune suppression, leading to the development of malignant melanoma and squamous tumors, along with photosensitivity, photodermatoses, photoallergies and the loss skin elasticity—which can lead to an increase in wrinkles.
In 1983, L. Kligman wrote about damage to the human dermis caused by chronic UV radiation.1 In this study, researchers exposed hairless mice to UV radiation and found that repair can occur if the skin is protected with sunscreens that provide UVB protection with an SPF of 6 and 15, in addition to UVA protection. Repair was found to occur in situ in severely damaged skin in the subepidermal reconstruction zones of new connective tissue, with parallel collagen bundles and a network of fine elastic fibers.
Gilchrest also provided a review of UV radiation damage and clinical repair.2 According to his review, skin loses elasticity and its metabolic activity slows with age. UV radiation exposure causes thickening of the epidermis and increased melanogenesis.