Scratch a dog and you'll find a permanent job. -Franklin P. Jones
Unless it requires vet intervention (and even then), my first action to pet skin and allergy symptoms is to start with changing what the pet consumes first! My experience is after that, there is a significant positive shift in health.
Most dogs foods sold in grocery stores, and even Pet Smart are high in fillers/by-products, dyes, formaldehyde, preservatives and even euthanized animals have been found in pet foods. Most dogs show symptoms by biting at their feet, yeast smelling ears or pink skin after years of consumption (and later health issues), but some dogs are sensitive from the beginning. There are many great formulas available at specialty pet stores and online. Acana, Orijen and other Canadian brands are typically a safe bet because the regulation in Canada for pet food are higher than the here in the USA.
Other brands like Natural Balance, V-Dog (what my dogs eat), Honest Kitchen and Holistic Select would be great foods to try.
The highest recalled foods and chemical filled are Ol’ Roy, Purina, Hills Science and Pedigree.
The treats may need to be eliminated as well.
During the food transition, (if the cause), you can use hemp oil and pureed pumpkin added to the diet to prevent and wet or dry stool issues.