Nancy Lee I have had four poodles (2 apricot colored, one silver and one black). My silver poodle at one time had a period where she would lick and bite at one of her front legs. This caused the fur in the area to turn black. The vet told me that there was nothing wrong with her leg and suspected that it was a "habitual thing" sort of like when someone bites their nails. Eventually she stopped on her own and the color eventually returned to silver. I'm not sure whether your poodle is just licking or maybe biting. I think rather than try and whiten his fur, maybe you could find the source of the licking or biting. Maybe he has skin allergies that are making him itch, or maybe it is just a habit like it was with my Ashley. Has your vet checked him out? Once the area is left alone it should return to its natural color. I was told to put something bitter tasting on the area but she actually stopped before I had to do that. Good luck!