itchy, panting cocker spaniel

Question
I have a 6 year old CS with no history of allergies.  About 2 months ago, he was in a fight with a raccoon and got a staph infection.  He was treated with antibiotics, steroid shot and an ointment to apply to the wound.  He healed up nice but began itchy terribly.  I took him back 2 weeks later for his checkup and they said it was probably rag weed allergies to give it time.  A few weeks later he was still itching and I took him back again.  They put him on another antibiotic and steroids.  It hasn't helped yet and we are almost done with the steroids.  He started panting yesterday like he is short of breath from running somewhere.  I tried feeding him yogurt for a possible yeast infection from the pills but he won't eat it.  I also switched his dog food from beef to fish/lamb combo.  This could be a beef allergy but takes 60 days to get out of his system I hear.  Any more suggestions?

Answer
I'm assuming this would has healed properly?  Is he itching all over or in specific spots?
How does his skin look?  Red?  Any bumps/rash?

I'm glad you're almost done with the steroids and antibiotics since I can't figure out why a vet would do this for itching.  It could very well be the steroids that are causing the panting.  In fact, it undoubtedly is the steroid.  I'd stop them now.  It's not working anyway.

Have you been bathing him?  Dogs absorb allergens through their skin so the first thing I'd advise is to give him a bath...rinse, rinse and then rinse more ending with cool water.
I want to know if this gives some temporary relief.  That will give some clues.

No Dermatologist would worry about a food allergy at this point since 95% of the time it's an inhalant allergy (a misnomer as I explained above).

As soon as he's done with the meds I'd definitely try an antihistimine and, at that time, I can tell you which one and dosage.  You have about a 40% chance this will work and it's well worth trying.

So first, try a bath..rinse like a maniac..and let me know what happens.  We'll go from there.
This can give relief anywhere from 4-5 hours to days and you may have to bath him every few days for a little while to get this under control.