Derma-IonX helps to relief symptoms of dry itchy skin and it helps the body to utilize the other supplements. I am not sure of the formulations you mentioned so make sure that you are giving digestive enzymes with meals and a probiotic such as Purina's Forti-Flora and a high quality fish oil daily. Try to avoid foods that the dog is allergic to, including treats. Sometimes treats are the worst offenders. If necessary, blood tests are available to help determine food sensitivities. You could also try a grain free novel protein food for a few weeks and then challenge with the suspected food to illicit a reaction.
You can also bathe your dog with our Defendex shampoo. It helps to soothe and cool hot irritated skin.
Hopefully, you don't have fleas in your environment that are keeping the immune system alarmed. If you have seen fleas, treat the environment, house, yard, car, wherever the dog has been.