UVA, damages collagen and thereby significantly accelerates aging of the skin. UVA and UVB destroy vitamin A in skin which may cause further damage. In general, UVA is the least harmful, but contributes significantly to the aging of skin, DNA damage and possibly skin cancer. It penetrates deeply and does not cause sunburn because it does not cause reddening of the skin (erythema) it cannot be measured in the SPF testing. Spectrophotometric testing measures the UVA blocking capability of sunscreens. As these test results indicate Brazilian Bronze is the most effective UVA block in the industry. It is important that sunscreens block both UVA and UVB.