Swelling under the tongue can result from a surprisingly wide range of causes, from a blocked salivary duct to a serious infection spreading through the floor of the mouth. Some are benign and resolve on their own; others, like Ludwig’s angina, can threaten your airway within hours. The floor of the mouth is a compact space sitting above the mylohyoid muscle, packed with salivary glands, ducts, blood vessels, and nerves, so problems in any of those structures can produce visible or palpable swelling beneath the tongue.
Salivary Stones and Duct Blockages
One of the most common reasons for sudden swelling under the tongue is a salivary stone, a condition doctors call sialolithiasis. The submandibular salivary glands sit just below the jaw, and each drains saliva through a long duct called Wharton’s duct that opens right under the tongue on either side of the frenulum. When a calcified stone forms inside that duct, it acts like a dam. Saliva backs up behind it, and the gland or the duct itself swells painfully, often becoming most noticeable during meals when saliva production ramps up.
Most salivary stones are small, but they can occasionally grow quite large. One published case documented a stone measuring about 6 cm in its greatest dimension lodged inside Wharton’s duct, causing significant local swelling and pain.1Cureus. A Rare Case of a Giant Sialolith Within Wharton’s Duct Smaller stones sometimes pass on their own, especially with hydration, warm compresses, and sour foods that stimulate saliva flow. Larger or impacted stones may need to be removed through a minor procedure, either by making a small incision in the duct lining or, in stubborn cases, by removing the affected gland entirely.
Ranulas and Other Cysts
A ranula is a type of pseudocyst that forms when a sublingual salivary gland is damaged or blocked, causing mucus to leak into the surrounding tissue rather than draining normally into the mouth. The result is a soft, translucent bluish swelling on the floor of the mouth that can look a bit like a frog’s belly, which is actually where the name comes from (rana is Latin for frog). Ranulas are painless at first, but they can grow large enough to push the tongue upward and interfere with eating or speaking.
Some ranulas stay put in the sublingual space. Others, called plunging ranulas, extend downward through or around the mylohyoid muscle into the neck, creating a mass that can be felt below the jawline.2PubMed Central. Atypical Multifocal Presentation of Congenital Plunging Ranulas: A Radiological Approach to Diagnosis and Treatment Treatment depends on how aggressive the ranula is. Less invasive options include marsupialization, where the cyst is opened and its edges sutured to the mouth lining so it drains continuously, and simple excision of the pseudocyst wall. However, these approaches carry meaningful recurrence rates, estimated at roughly 21% for marsupialization and 11% for pseudocyst excision. Removing the sublingual gland itself has a much higher cure rate, around 99%, and is the go-to for ranulas that keep coming back.3PubMed Central. Surgical Treatment of Sublingual Gland Ranulas
Mucoceles, which are smaller mucus-retention cysts, can also appear on the floor of the mouth, though they are more common on the inner lip. These tend to be tiny, dome-shaped, and painless. They often rupture on their own and refill, sometimes repeatedly, before eventually resolving or being removed.
Infections and Ludwig’s Angina
Infections in or around the floor of the mouth are a more urgent cause of sublingual swelling. A tooth abscess, particularly from a lower molar, can spread into the deep spaces beneath the tongue. When this infection involves both sides of the floor of the mouth and the tissue under the chin, it is called Ludwig’s angina, a rapidly progressive cellulitis that can obstruct the airway and spread through tissue planes into the neck and even the chest.4Cureus. Importance of the Physical Exam in Diagnosing Ludwig’s Angina Without Access to Modern Imaging Modalities in the Developing World
Ludwig’s angina is a true emergency. The swelling is firm (not squishy like a cyst), painful, and accompanied by fever, difficulty swallowing, and sometimes an elevated or protruding tongue. The infection often originates from a periapical lesion of a lower molar, making a thorough oral examination critical in anyone presenting with a neck mass or floor-of-mouth swelling.5Europe PMC. Ludwig’s Angina: The Importance of Oral Cavity Examination in Patients with a Neck Mass Treatment involves high-dose intravenous antibiotics and, in many cases, surgical drainage. Securing the airway is the first priority because the swelling can close it off rapidly.
Less dramatic infections can also cause sublingual swelling. An infected salivary gland (sialadenitis) from a blocked duct, a bacterial or viral infection of the sublingual soft tissue, or even a dental abscess that has not yet spread can all produce localized swelling, redness, and tenderness under the tongue. These still warrant prompt medical attention, but they do not carry the same airway risk as Ludwig’s angina.
Allergic Reactions and Drug-Induced Angioedema
Sudden swelling of the tongue, the tissue beneath it, or both can be a sign of angioedema, which is deep swelling in the tissue layers below the skin or mucous membranes. Food allergies, insect stings, and latex exposure are classic triggers, but one of the sneakier causes is medication, particularly a class of blood pressure drugs called ACE inhibitors (lisinopril, enalapril, ramipril, and others).
ACE inhibitor-induced angioedema is uncommon but well documented, and what makes it tricky is that it can appear years after you first started the medication. It typically causes bilateral swelling of the face or throat, but cases of one-sided tongue swelling have been reported, which makes diagnosis harder because it can mimic other conditions. One published case involved a 77-year-old man on long-term ACE inhibitor therapy who developed sudden unilateral tongue and lip edema.6Cureus. Unilateral Tongue and Lip Edema: A Rare Presentation of Angiotensin-Converting Enzyme (ACE) Inhibitor-Induced Angioedema The swelling resolved after the drug was stopped, but angioedema involving the tongue or floor of the mouth can be life-threatening if it progresses to airway compromise. If you take an ACE inhibitor and experience sudden oral or facial swelling, seek emergency care even if the swelling seems mild.
Hereditary angioedema, a genetic condition involving deficiency of a protein called C1 inhibitor, is another possible cause. It tends to produce recurrent episodes of swelling in the extremities, face, or gut, and oral involvement, while less common, does occur. Unlike allergic reactions, hereditary angioedema does not respond to standard antihistamines or epinephrine, which is an important distinction for treatment.
Trauma and Sublingual Hematomas
Injury to the floor of the mouth, whether from accidental biting, a fall onto the chin, a sports impact, or dental procedures, can cause bleeding into the sublingual space. The resulting collection of blood, called a sublingual hematoma, can swell rapidly and push the tongue upward. This is more dangerous than it sounds. The sublingual space is relatively confined, and a large hematoma can compromise the airway much like Ludwig’s angina does.
Dental procedures are a recognized trigger. Sublingual hematomas have been reported as a potentially lethal complication following mandibular implant placement, where the drill or implant damages a blood vessel in the floor of the mouth.7Europe PMC. Life-Threatening Sublingual Hematoma after Mandibular Implant Placement Tooth extractions have also been implicated. In one case, blunt trauma during extraction led to a traumatic pseudoaneurysm of the lingual artery that ruptured about a week later, producing a rapidly expanding, life-threatening sublingual hematoma.8Annals of Case Reports. Life-Threatening Sublingual Hematoma and Traumatic Lingual Artery Aneurysm after Dental Extraction
People on blood-thinning medications (anticoagulants like warfarin or direct oral anticoagulants) are at higher risk of sublingual hematomas from relatively minor trauma. In rare cases, the bleeding can be spontaneous. Acquired hemophilia A, an autoimmune bleeding disorder caused by antibodies against clotting factor VIII, has been reported as an unusual cause of spontaneous sublingual mucosal bleeding.9Cureus. Unusual Cause of Sublingual Hematoma Compromising Upper Airway: Acquired Hemophilia A If swelling under the tongue develops rapidly after a dental procedure or an injury, especially if you are on anticoagulants, get evaluated urgently.
Vascular Malformations
Venous malformations are tangles of abnormally developed blood vessel channels that are present from birth, even if they do not become noticeable until later in life. When they occur in the tongue or the floor of the mouth, they can cause a soft, compressible swelling that may change size with body position or straining. Unlike hematomas, vascular malformations grow slowly and are typically painless unless a complication develops.
The main risks of oral vascular malformations are bleeding, airway obstruction if the malformation grows large enough, and difficulties with chewing, swallowing, and speech.10PubMed Central. Localization and treatment of lingual venous and arteriovenous malformations Venous malformations in particular can develop blood clots within their abnormal channels, a condition called phlebothrombosis, which may cause sudden pain and increased swelling.11Europe PMC. Vascular malformation of tongue with phlebothrombosis/phlebolith in a young patient: an unusual presentation Treatment options range from sclerotherapy, where a chemical is injected to shrink the malformation, to surgical excision, depending on the size and location.
Benign and Malignant Tumors
Growths in the floor of the mouth, the sublingual glands, or the tongue itself can present as gradual, painless swelling that you might not notice until it reaches a certain size. On the benign side, pleomorphic adenoma is the most common benign tumor of both major and minor salivary glands.12PubMed Central. Pleomorphic adenoma of the tongue: A common entity at the uncommon location It typically presents as a firm, slow-growing, painless lump. While pleomorphic adenomas involving the tongue itself are rare, they do occur and can cause noticeable sublingual or lingual swelling.
Dermoid cysts are another benign possibility. These are developmental cysts that form from trapped skin cells during embryonic development. When they occur in the floor of the mouth, they tend to grow slowly in the midline and can push the tongue upward. Imaging sometimes shows a characteristic pattern of calcified material inside the cyst.13Europe PMC. Dermoid Cyst of the Floor of the Mouth: Diagnostic Imaging Findings
Malignant tumors are less common but more concerning. Adenoid cystic carcinoma is a slow-growing but aggressive cancer of the salivary glands that can arise in the sublingual gland or the minor salivary glands scattered throughout the floor of the mouth. It tends to present as a slowly enlarging swelling, sometimes without ulceration, making it easy to dismiss initially. One case involved a 58-year-old man with a growing swelling on the right side of the floor of his mouth that had been present for just one month.14PubMed Central. Adenoid cystic carcinoma of the sublingual gland: A case report Adenoid cystic carcinoma has a tendency toward spreading along nerves and recurring after treatment, and it is associated with distant metastasis, most commonly to the lungs.15PubMed Central. Submandibular and sublingual salivary gland involvement in adenoid cystic carcinoma Squamous cell carcinoma, the most common oral cavity cancer overall, can also arise on the floor of the mouth and present as swelling, an ulcer, or both. Any new, painless lump under the tongue that persists for more than two weeks deserves a clinical evaluation.
Systemic and Metabolic Conditions
A few whole-body conditions can cause swelling in the sublingual area as part of a broader pattern. Amyloidosis, a group of diseases where abnormal proteins deposit in tissues throughout the body, frequently affects the tongue and mouth when it involves the oral cavity. The tongue and the lining of the cheeks are the most commonly affected sites, and the swelling tends to make the tongue enlarged, hardened, and stiff, a presentation known as macroglossia.16PubMed Central. Oral amyloidosis: an update Oral amyloidosis is usually secondary to systemic disease rather than an isolated finding, so the sublingual swelling typically appears alongside other symptoms like fatigue, kidney problems, or heart issues.
Other systemic conditions that can sometimes produce sublingual or lingual swelling include hypothyroidism (which can cause a generalized puffiness including the tongue), granulomatous diseases like sarcoidosis, and certain nutritional deficiencies. These are much less common causes than salivary stones or infections, but they are worth considering when a straightforward local explanation does not pan out.
Radiation Damage to Salivary Glands
People who have undergone radiation therapy for head and neck cancers face a distinct set of problems with the salivary glands. Radiation causes collateral damage to glandular tissue, leading to complications including mucositis (painful inflammation of the mouth lining), xerostomia (dry mouth), and reduced saliva production.17Europe PMC. Radiation-Induced Salivary Gland Dysfunction: Mechanisms, Therapeutics and Future Directions While the dominant symptom is dryness rather than swelling, the damaged glands can become inflamed and swollen, particularly during and shortly after treatment. Chronic radiation-induced changes can also make the glands more susceptible to infections and stone formation down the line. Despite advances in targeting radiation more precisely, long-term glandular damage remains a significant problem for many survivors, and current treatments provide temporary relief without reversing the underlying tissue destruction.
When to Worry and What Happens Next
Not every bump under the tongue is an emergency, but a few patterns should send you to a doctor or emergency room quickly. Rapidly expanding swelling after a dental procedure or injury, especially if it pushes the tongue up or makes breathing feel tight, needs urgent evaluation because of the airway risk. Floor-of-mouth swelling with fever, difficulty swallowing, and a “woody” firmness (classic signs of Ludwig’s angina) is a genuine emergency. Sudden tongue or sublingual swelling in someone on an ACE inhibitor should be treated as angioedema until proven otherwise.
For slower, painless lumps, the timeline matters. A soft, bluish swelling that appeared over days or weeks and fluctuates in size is more likely a ranula or mucocele. A firm, fixed mass that has been growing steadily warrants imaging and often a biopsy to rule out a tumor. Doctors often start with a physical examination and may use ultrasound as a first-line imaging tool because it is quick, inexpensive, and good at distinguishing fluid-filled cysts from solid masses. For deeper or more complex lesions, CT or MRI scanning may be needed to assess how far the swelling extends into surrounding structures.18Radiographics. Imaging the floor of the mouth and the sublingual space The sublingual space is bounded below by the mylohyoid muscle, which separates it from the submandibular space in the neck, and understanding whether a mass has crossed that boundary changes both the diagnosis and the treatment plan.19SA J Radiol. Imaging evaluation of the benign and malignant lesions of the floor of the mouth: Pictorial review
The reassuring reality is that most sublingual swelling turns out to be something manageable: a salivary stone that can be coaxed out, a ranula that can be drained or excised, or a minor infection that responds to antibiotics. The key is recognizing the handful of scenarios where the stakes are higher and acting on them quickly.