Hi. Thanks for posting your concern at HCM I would keep a possibility of Drug Induced Urticaria, to probably pain killers (NSAIDs) that he may be taking post surgery. Urticaria OR hives can occur due to various causes like(to name a few): -Infections(bacterial , viral, fungal) -Drugs(NSAIDs/pain killers) -Certain foods -Cold temperature -Cholinergic Urticaria:in response to strong emotions, exercise -Physical Urticaria: dermographism, pressure (prolonged standing, sitting) -In autoimmune disorders like SLE, RA etc. -A few cases have no underlying cause and are known as idiopathic urticaria. As a treating doctor i would have advice him to get few basic lab tests like Hemogram, stool for ova/cyst, Urine routine, Chest Xray. An oral antihistamine like Fexofenadine OR Loratadine once or twice daily for a week would be suitable. They are non-sedating and wont affect alertness level. a topical soothing lotion like calamine would help him symptomatically. regards