Your 9 year old has asthma ,which is in itseldf an allergic condition or called atopic state .Hives a a part of allergic. spectrum .He is having the hives as a part of his allergy and asthma both caused by an infection either by bacteria or by virus .He is on appropriate management namely antibiotics ,steroid under antibiotic cover and antihistaminic ---all three are necessary at this point in time .What should be done at this point is to keep a wtch on the way air is moving in and out of his chest ,monitor his state of alertness and if avaiable a Blood gas analysis to see his oxygenation and carbon dioxide level. the answer to your question is that hives can occur in an atopic child .But be reassured the whole episode will respond to the medications given.