Broad-spectrum sunscreen protects against the harmful effects of both UVA (aging rays) and UVB (burning rays). To be classified as offering broad-spectrum protection, a product needs to absorb or reflect at least 90% of the UV rays. All Sun Bum Sunscreens offer broad-spectrum coverage. UVA rays penetrate the skin more deeply than UVB rays and are primarily responsible for premature skin aging and wrinkling. UVA rays have also been shown to cause skin damage at the cellular level. UVB rays damage the outer layers of the skin. They are the main cause of sun burn and play a key role in the development of skin cancer.