If a patient experiences swelling and pain on one side of the face, there are many diseases that need to be considered, commonly including oral inflammation, mumps, local lymph node inflammation, boils or carbuncles on one side of the face, etc. 1, oral inflammation: for example, periodontitis or oral ulcers aggravate the inflammation, which spreads to one side of the facial soft tissues, causing inflammation of facial tissues and the symptom of one side of the face is swollen and painful. 2, mumps: it is caused by the mumps virus, which grows and reproduces in lymphatic tissues and leads to local inflammation. Mumps: caused by the mumps virus, which can grow and multiply in the lymphatic tissues and lead to local inflammation, and after entering the bloodstream, the inflammation can spread, and when it spreads to the side of the face, it will cause swelling and pain; 3. Local lymph node inflammation: if the lymph nodes involving the lower jaw and the upper part of the neck are inflamed, when it is severe, it may affect the face, and inflammation may occur, which may cause swelling and pain on the side of the face; 4. Other: if there are boils or carbuncles on the side of the face, the main clinical manifestations of the two is that they will have redness and swelling, hardness, and pain, which may cause swelling and pain. The main clinical manifestations of boils and carbuncles are redness, swelling, hard nodules, and pain, which can lead to swelling and pain on one side of the face.