Welcome in H.C.M. for consulting.
I have gone through your query regarding red and swollen of your son which is painful and not responding to anti allergic and cortisone
Considering all aspects of complaints, and effects of medication given to your son it appears as your son is suffering from infective perichondritis
of pinna. Because allergic swellings are usually associated with itching and painless, while your child is having swollen ear which hurts therefore it appears to be infective thus addition of antibiotics is supposed to be necessary in treatment.