A likely reason for having a large bubble under the tongue is a mucocele, wherein a damaged spit gland causes a soft protuberance or a blister-like lesion to form in the mouth, explains NetWellness. Mucoceles may also occur on the lips and on the palate.
While mucoceles can be bothersome to some individuals, it is a benign condition that commonly occurs in many people. It results from a small injury to the duct, which is a tiny tube that transports saliva from the salivary gland to the mouth’s surface. Biting and other accidental traumas can lead to such injury.
When the duct is injured, the damaged gland releases a thick saliva into nearby tissues instead of sending the mucus-type saliva into the mouth along with other saliva, explains NetWellness. The buildup of saliva causes the formation of a bubble or blister that either looks clear or bluish. Poking or injuring the blister can result in bleeding within the accumulated pool of saliva, thus making the blister appear red or purple.
It is typical to experience enlarged, broken or shrunken lesions that occur persistently. The lesions tend to swell, tear and heal repeatedly, and they do not resolve without medical treatment. Oral surgeons usually treat the condition by removing the affected gland and the entrapped saliva.