The possible reasons for the swelling reaction after wisdom teeth extraction include greater trauma, postoperative infection, blood seepage, etc., as follows. 1. Larger trauma: some wisdom teeth need to be flapped to remove the bone when they are extracted, and too much trauma when flap is flipped or too tight suture after flap is flipped, which may lead to swelling after tooth extraction. 2. Post-operative infection: bone fragments, tooth fragments, tartar, granulation tissue in the extraction wound may lead to infection of the extraction wound, which can be seen as blood swelling of the wound. 3. Blood seepage: If blood seepage occurs in the wound, hematoma will occur if the blood flows into the gap, and ecchymosis can be seen in the anterior cheek and submandibular region. There may be other reasons for the swelling after wisdom teeth extraction, so it is recommended to go to the hospital in time.