Thank you for posting on HCM. The condition you have referred to is called urticaria or hives. Its an allergic manifestation of skin, where an allergen leads to release of certain substances from your blood, leading to itchy skin rash and swelling over soft tissues. In your case either the staph. infection or drug Bactrim could be the probable causative agent. Its proper management requires thorough history including drug history, clinical and laboratory work-up. As for treatment part, best would be the avoidance of allergen as far as possible. I might consider providing you a list of probable drugs which can lead to allergy and thus should always be presented to doctor during consultation. I would recommend you safer antibiotic like Azithromycin to take care of your infection and advise you various anti-histaminics with or without oral corticosteorids. Hope this will help you in resolving your query. Thank you Dr Hardik Pitroda