A parulis is commonly called a “gum boil”. It is caused by an infection around a tooth root that has expanded to the point that it has burrowed through the outer layer of the bone and has begun to seep into the mouth. This tooth infection can be started by a deep cavity, or fracture of the tooth, or by a severe gum pocket that has caught some food in it. With infections, the body tries to ward off the onslaught of bacteria by sending an army full of white blood cells to the area. As these white blood cells and bacterial sludge collect, they will put pressure on the surrounding tissues, in this case bone. Since bone is very sturdy, initially, the infection will put pressure on nerve endings causing much pain. As the pressure builds, the bone will begin to erode. At this point, the bone has been weakened and begins to expand. The resulting pus will find the weakest point and break through the bone. At this point, there is usually major relief of pain since the pressure has been relieved inside the bone. Just because the pressure has been relieved doesn’t mean that the saga is over. The source of the problem must be addressed, that means either doing root canal treatment, gum treatment, or extraction.