** Thanks for contacting with your health concern 1. As there is no history of being bitten nor of any food allergy, thus one has to think of other possibilities which can cause build up of fluid or inflammation inside the lip tissue like: . cold sores [herpes] . cheilitis . since swelling is there in other parts of the body could be environmental allergy which is most of the time unavoidable [like pet dander, pollens, mold spores, dust] 2. It is wise to consult an allergist who will perform skin or blood tests to determine what you’re allergic to, and based on the results, they may recommend an over-the-counter or prescription antihistamine or allergy shots. PS. Several things can cause your lips to swell, from common allergies to rare genetic conditions, remain under the regular supervision of your healthcare provider to figure out the underlying cause so you can treat it or avoid it in the future.