Mali Uromastyx lizard

Question
hello, I have a question... We have a mali uromastyx lizard, and not that long ago we've noticed that he's got these little patches of grey spots on his skin. I don't know if it's because he is dry, or what, but we did take him to a vet and they took some tape, put it on his skin and did some test with it or something, and they said it's okay. I just wanted a second opionion because they busted out a book and had no idea what they were talking about. We know he is a desert lizard, and it gets really hot, but I've read that they will get sick if they get wet because of the moisture. Help please!!

Answer
 Malis get enough water from their food.  The first thing I think of when lighter patches appear on a lizard hide is the normal start of a shed, where old skin starts to lift, giving a gray appearance.  Shedding is a normal sign of growth and a full adult will still shed once or twice a year.