The term "sun protective" describes fabrics specifically designed to protect the skin from UV radiation. and it contains UV absorbent .While it makes sense that clothing protects skin from the sun, early research reveals that many summer fabrics offer too little protection.
The two most important features of sun-protective fabric are tight construction and color. Openings between the yarns allow UV radiation to pass through the fabric and reach the skin, so tightly woven or knit fabrics provide the best coverage.
Dark colors provide the highest protection levels. This sounds contradictory to the traditional advice that dictates wearing whites or light colors in warm weather. Heat and visible light are reflected from these light colored fabrics, but UV radiation passes through to the skin. Darker colors, such as navy, black, dark greens and reds, block more harmful UV rays.
Some of the earliest and most effective fabrics on the market were simply made of tightly woven, lightweight nylon or polyester. There were no special chemical treatments. Synthetic fibers are non-absorbent, so they could be worn while participating in water sports without getting heavy and dry quickly with little or no wrinkling.
More recently chemical sun blocks have been added to lightweight fabrics to offer a wider fabric range with good UV protection. These chemicals remain effective after many launderings.