There are two types of UV rays in sunlight – UVA and UVB rays – both of which are harmful to your skin. UVA rays penetrate deep into the layers of the skin and are known to lead to early skin aging. UVB rays are the primary cause of sunburn. They penetrate the surface of the skin and cause damage to the skin cells. Both UVA and UVB rays can contribute to skin cancer. While both cause damage to the skin, UVB rays account for 80 percent of skin damage, including certain skin cancers, sunburn and skin aging.
SPF measures protection against sunburn caused primarily by UVB rays. For the first time, the FDA offers a test that measures the breadth of the UV protection, which includes both UVA and UVB. Products that pass the new test may be labeled as Broad Spectrum. Together with SPF values, the new labels provide additional information regarding a product's overall protection against UV rays.
Sunscreens that are not broad spectrum or have SPF values between 2 and 14 must have a warning that the product has not been shown to help prevent skin cancer and early skin aging.