Hi.. Thanks for the query.. Hives on the body with severe itching seems to be most probably due to allergic reaction and in case if you are taking Gabapentin since long back the symptoms appear then it can be probably not related to the drug.. Other causes of itching and hives can be due to allergy to any food, detergents, soap, poison ivy, leather, latex etc.. I would suggest you to consult an Allergist and get evaluated and a thorough clinical evaluation and investigations like allergic tests like Patch test, RAST test, food challenge test etc can help in diagnosis and treatment can be done accordingly.. The tests will help in ruling out the exact cause of the allergen and once you know the cause of the allergic reaction you can avoid exposure to it to prevent allergy attack.. The allergist can advise to oral anti allergics as well as injectable steroids for relief.. As of now you can take anti-allergics like Levocetrizine, Allegra to control the itching and swelling.. Do cool compresses.. Application of calamine lotion can help in soothing the skin.. You can also be instilled an Immunotherapy that will help in reducing the severity and frequency of allergic attack.. Hope this helps.. Regards..