Hi.. Thanks for the query.. It seems that the swelling of half of your upper and lower lip without any trauma or any other problem seems to be most probably be due to allergic reaction to any unknown allergen.. I would suggest you to take an anti allergic medication like Allergra or Benadryl.. Do cool compresses over the lips.. In case if there are repeated episodes of the same symptoms you should consult an Allergist and get evaluated and a thorough clinical evaluation and investigations like Prick test, Patch test, RAST test can help in diagnosis and treatment can be planned accordingly.. You can be advised anti allergic medications and if needed steroids as well as once the cause of allergy is ruled out avoid exposure to the allergen to prevent allergic symptoms.. Hope this helps.. Regards.