Pups that are sensitive to grains can have a negative reaction to oatmeal.
How Often Should You Bathe Your Pet? Also avoid shampoos that include oatmeal. Oatmeal has a great reputation as a soothing ingredient, but in animals that have a problem with grain (which is 80 percent plus of allergic dogs!) they are likely to have problems with oatmeal shampoos. Grain-based shampoos may also provide a carbohydrate food source for unwanted yeast and bacteria. The only pets that truly benefit from oatmeal shampoos are those that have poison oak or poison ivy reactions.
Do you use a conditioner? A good conditioner is great for keeping their hair & skin soft. This thread has a slideshow of skin problems in dogs, maybe it will help, as you'll want to rule out any medical issues.
http://www.yorkietalk.com/forums/die...lems-dogs.html