Some of my dogs have this as well. It is protein stain from licking. When it shows up where Maddie's has, that's generally the case. they also have sweat glands in their feet and the ones between the pads can be caused from this as well. Barb Bowes Bo & Chelsea (Pyrs) & Flopsy (Pyrenean Shepherd) "The more people I meet, the more I like my dog!" bamb@monmouth.com