Try a different shampoo & conditioner, one w/out oatmeal. Dogs that are sensitive to grains do not do well on oatmeal shampoo...They do have coconut cleanser based shampoos, like Espree. Get the Silky Show set, it's on sale right now @ petco.com.
Espree Natural Silky Show Dog and Cat Shampoo at PETCO Espree Natural Silky Show Pet Conditioner at PETCO