I suggest you read Callie's post again.  As others, including myself have said, this is often a two part problem. Ignoring the allergy issue and only dealing with it behaviorally won't solve the problem if he is itchy due to allergies.

 Pedigree is not a good quality food.  Here's a link so you can educate yourself on dog foods in case you want to try something a bit better.  The cost will be higher per bag but you will feed less and your dog will poop less and be healthier.

http://www.dogfoodproject.com/

 

If you suspect an infection again it needs to be treated.