ORIGINAL: loogout1

The way I understand it, and I'm no genius, is that the fabric used in most clothing is treated with UV brighteners, a dye if you will. This brightener makes whatever other colors are used on that fabric brighter and more vivid. The UV brightener also protects the fabric(thus the reflection of the UV rays) from UV rays since they will make the fabric break down quicker. The UV killer spray just basically coats the garment eliminating the reflection of the uv rays. When you wash the treated clothes you must re-apply the treatment. I dont know if it works or not but any advantage I can get I'll try it out. No harm no foul.