There are several main reasons for swollen gums: 1. Gingivitis and periodontitis are the most common causes of gum swelling and pain, mostly due to poor oral hygiene and incomplete cleaning resulting in plaque and calculus buildup, which causes stimulation of the gums to form inflammation and the symptoms of gum swelling and pain. Gingivitis includes adolescent gingivitis, gingivitis during pregnancy, and medication gingivitis, all of which can cause swollen gums. The drugs include the anti-epileptic drug phenytoin sodium, the anti-immune drug cyclosporine, and drugs for hypertension such as nifedipine may cause swollen gums; 2, systemic diseases such as gingival fibromatosis, which is hereditary in families, and others such as leukemia, scurvy, hemophilia, etc., can also cause swollen gums and bleeding symptoms; 3, food impaction: if the gap between the teeth is large or the edges of the dentures do not fit tightly, it is easy to cause food impaction when eating. If you do not pay attention to cleaning time will cause inflammation, which leads to swollen gums, pain, often accompanied by bad breath; 4, periapical inflammation: will also cause swollen gums, pain.