What can i do? for my dog,s dry skin (shih tzu)

Some tips (without knowing any details of your pet specifically):
– do not bathe your dog too often; keep his coat clean but that is all—this will help with scratching and, also, keep them from being uncomfortable during winter months. Water and winter do not mix well with your pet.
– brush your dog often to remove dead hair and dander; if possible, a quick brushing every day will help your dog a lot.
– when you must bathe your dog, be sure to use a dog shampoo. A dog’s ph level is different from our own and human shampoos can be harsh on their skin. Buy a dog shampoo that can offer moisturizing effects. Besides providing moisture, many shampoos can also offer flea and parasite protection, which can also help lessen scratching.
– by using quality foods and adding fatty supplements to their food (oil, etc), you can ensure that their skin/coat is flake free

If you notice anything out of the ordinary on his skin, be sure to call the vet ASAP. This includes redness, bumps, rashes or other unusual inflammations, open sores, or hair falling out excessively.

Hope this helps!