There are many reasons for swollen and painful gums, such as oral diseases, poor hygiene, blood system diseases and so on. 1. Oral diseases: Many oral diseases can manifest swollen and painful gums, such as periodontitis, gingivitis, wisdom teeth pericoronitis, etc., which may cause some damage to the gum tissue, and then the phenomenon of swollen and painful gums. 2. Poor hygiene: Poor oral hygiene can lead to plaque and calculus around the gums, which can stimulate inflammation of the gums, resulting in swollen and painful gums, which can be accompanied by bleeding. 3. Blood system diseases: acute myeloid leukemia and other blood system diseases, due to the blood system malignant cloning caused by gum hyperplasia, enlargement of the gums, oral mucosa and gum bleeding, or the phenomenon of necrosis of the gums, can cause swollen and painful gums. There are many reasons for swollen and painful gums, after the appearance of symptoms, it is recommended to go to the hospital in a timely manner to improve the examination, under the guidance of a professional doctor to take standardized treatment, do not ignore the symptoms, take it lightly.