Hello and Welcome to Ask A Doctor service. I have reviewed your query and here is my advice. Hives like bumps on wrists and forearms that developed circular purplish area 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.. It can also be due to any bug bites while taking shower. If it gets better you need not to worry but in case if it recur or spreads even this time then I would suggest you to consult an Emergency room and get evaluated and a thorough clinical evaluation and investigations like allergic test 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.. Hope I have answered your query. Let me know if I can assist you further.