My name is***** and I am sorry to hear that your dog is so itchy.
When I see an itchy dog, I usually think of the following things:
1) Environmental allergies. Treatments can include prednisone or antihistamines, but can also involve the following- frequent (3x weekly bathing to physically wash off the allergens), fish oil supplements, antioxidant supplements and topical cortisone sprays on the affected areas. You can use prednisone long term if you use a low enough dose, I would aim for about 0.5mg/pound of dog maximum per day. There is also a medication called Apoquel that can help and there is a new injection that should be available this winder. You can also consider allergy testing and allergy shots. These treatments are available through your regular veterinarian or you can consider taking him to a dermatologist.
2) Food allergies. These are also common. I would recommend a food trial with a hydrolyzed protein diet (Science Diet, Royal Canin and Purina all have varieties of these formulas.) These diets also have a variety of other ingredients that can also help the skin and reduce the severity of environmental allergies.
3) Fleas. Fleas are a very common cause of itchiness in dogs. I would ensure that your dog has good flea control as the first step. Good over-the-counter products include Frontline Plus, Advantage, and the Seresto collar.
4) Mange. This is a much less common cause of itchiness in dogs. Your veterinarian can diagnose this with a physical exam and a skin scrape.
Does this help? What other questions do you have?