The first question I get when people see SPF Addict sun protective clothing is "I thought my own clothes were protecting me"? Second question is "How do these clothes protect me"?
Tan lines can be deceiving outside your clothing, giving you the impression that your clothes have you completely protected from the sun. The truth is that you are somewhat protected, meaning your fabric may in fact be a UPF (ultraviolet protective factor) 5 to 10, thus explaining the tan line you have outside your shirt. This rating would NOT be near what you need to keep you sun safe from potential skin cancer and premature aging.
This is extremely important to be aware of if you are photosensitive from the sun.
Ultraviolet indeed passes thru your fabric just as it passes thru windows and clouds, in particular the long wave length known as the UVA rays.
Sun protection has become an important part of life today because the rate of skin cancer is rising rapidly.
Next time your shopping look for a UPF rating of 50+ on the tag. This is the highest rating for sun protection in fabric. UPF50+ blocks 98.8% of the sun's ultraviolet rays.