I'm not sure about the paw area's turning red but around the mouth, the fur is turning reddish pink because of the PH balance and bacteria or minerals found in the drinking water. If you have ever used a plastic drinking bowl for your shih tzu, you may notice after a day or so that a reddish film gets inside the bowl. This is the same stuff that gets on the fur. I have heard that adding a drop of organic apple cider vinegar(Bragg is the most popular one found at health food stores) to the drinking water will remedy this problem. Also, giving your shih tzu a tablespoon of plain yogurt a day can fight off this bacteria as well.
