Do laundry detergents that add sun protection to clothes really work?

Clothing’s ability to block the sun’s age-inducing rays largely depends on how tight the weave is:  the tighter the weave, the better it blocks out the sun.  A simple way to test a piece of clothing is to hold it up to the sun and look to see how much light shines through:  the more light that shines through, the worse the protection.  An average T-shirt blocks about 70% of the sun’s rays, while jeans block out 100% (think about it:  when was the last time you got a sun burn under your jeans!).  Clothes that have a “UPF” label (like Coolibar brand), which stands for Ultraviolet Protection Factor, have undergone testing to ensure the product’s sun blocking claims are accurate.  An easy way to determine how much protection your getting is simply divide 1 by the UPF, which equals the amount of light that is unblocked.  For example, a T-shirt with a UPF of 50 lets 2% (1/50=2%) of the rays through.  In other words, it blocks 98%.  A UPF above 30 is generally recommended.  UV protecting laundry detergents, like Rit Sun Guard, add microscopic white crystals to clothes with one washing.  This decreases the amount of light that penetrates through the fabric to hit your skin.   The invisible crystals stay on the fabric for about 20 regular washes.  This detergent can bring the UPF of an everyday T-shirt from 5 to 30, taking the amount of light blocked from 70% to 97%.  Over time, this simple step can really help keep your skin from prematurely aging.