I am so sorry your boy has this.
These can be hot spots, pyoderma or impetigo if there are any sores.Please compare to this link:
What you can do is go to your local pharmacy and get some Burrows solution. This is drying agent. Many time you will find it in a name brand called Domeboro. Just ask the pharmacist what brand names they use. This is used for hot spots. It will help fight infection and decrease itchiness. Clip the hair away in the areas as well before using the drying solution.
Use an antiseptic shampoo called Chlorhexiderm. This in combination with the burrow's solution, will heal hot spots and relieve dryness and itching.
I hope he feels better very soon.