There are two kinds of
skin-damaging ultraviolet rays. Long wave UVA rays and medium wave UVB rays.
Both are harmful and link to skin cancer and aging. UVB rays cause sunburns. UVA
rays penetrate windows and are responsible for tanning and premature aging.
UPF refers to the Ultraviolet
Protection Factor UPF which is a measurement of the amount of UVA
and UVB rays that a fabric blocks.
SPF refers to the Sun
Protection Factor which is a measurement of the amount of UVB rays
a sunscreen lotion will block. The lower
the number, the faster you’ll burn. Sunscreen should be reapplied regularly, at
least every two hours.