A suntan may repel some UV rays, but research shows that the protection of a natural tan is only equivalent to SPF 4. And don’t let those clouds fool you; as much as 80 percent of the sun’s rays still reach the earth on an overcast day. Any bare exposure to sun (whether the results are red or brown) promotes cellular damage.
Fascinating Fact: SPF 15 products block more than 93 percent of UVB rays. SPF 30+ blocks 97 percent+ of UVB rays.