I'm no Vet. but it looks just like a food allergy. What kind of food do you feed him? I would go with either home cooked (which is the very best) or a premium kibble that does not have grains, by-products, meals and such which is garbage and just fillers. The first three ingredients listed on pet foods are the main ingredients.
http://www.nexusmagazine.com//Petfood.html
http://www.homevet.com/petcare/foodbook.html http://drjackie.freeservers.com/arti...ven_a_dog.html