Hi, Itchy welts on random places over the body with itching seems to be most probably due to allergic reaction and in case if you have not changed any shampoo, soap or laundry etc., then it seems to be most probably due to any food or medication 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 Levocetirizine, Allegra to control the itching and swelling. Do cool compresses. Application of calamine lotion can help in soothing the skin. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician