Carmi at Reactor Panel in Oakland told me about this, it's some kind of enzyme reaction thing. I haven't tried it yet, but she said after she sprayed it on her horses tail, she could see the tail get whiter each day after that for a while. I looked it up online here's what it says: WOW! is a unique horse product. It removes grass and manure stains, turns yellowed tails, manes and feathers white, and restores the natural color of light-colored manes and tails (e.g. Palominos, Paints, etc.). WOW! is NOT a bleach, a dye, or a stripping agent, nor a messy purple or bluing shampoo or coloring. Its natural brightening ability is due to proteolytic action and non-ionic bond separation, breaking the bond between hair and the protein of dirt, grime, urine, feces, dust, etc. that discolors horse hair, manes, tails, and equine feathers.
WOW! is an easy-to-apply, natural, and biodegradable product. Simply spray it on and either rinse it out or leave it in for sustained action. Fresh peppermint scent. Available in a 32 oz. bottle