You are suffering from what Dermatologist call urticaria. Common causes are food allergy, infection or drugs taken for some condition. It presents with itching resulting in formation of red rashes which we call hives or wheals. Although in most cases cause remains unknown in spite of a thorough search. You have done allergy testing so you can start avoiding these and see. I have never got success in this. Urticaria should be symptomatically treated with antihistamines so that you do not get any new hives. The treatment should be prolonged until it resolves which usually takes 1 to 6 months. Please call me or contact me through online consult option for further details and treatment. ,