How Allergic Reaction To Amoxicillin Be Treated?

My 4 year old son was taking amoxicillin for strep 9 days before bad hives formed. Benadryl chewables, oatmeal baths, and benadryl cream for the itching is what hes taking. Took him to the hospital 24 hours after first sign of hives. They said his airways would be ok because nothing happened to them yet and its been 24 hours. Is that true? They did not give steroid either. Its now been 62 hours since hives appeared. Hes in pain, his hands are itching terribly, His throat hurts, and hives are from head to toe. Hes not eating much and hes taking to hewable tabs every 6 hours. He also vomitted twice in the last 2 hours but nothing came out. Do you have any advice?