A swollen submandibular gland, the walnut-sized saliva gland tucked beneath each side of your jawbone, is most commonly caused by a blocked salivary duct or a bacterial infection. These two causes account for the vast majority of cases, though autoimmune conditions and, less commonly, tumors can also be responsible. The submandibular glands produce about two-thirds of your resting saliva, and their anatomy makes them particularly vulnerable to blockages.
Salivary Stones: The Most Common Cause
Salivary stones, called sialoliths, are the single most frequent reason a submandibular gland swells up. These are small, hard deposits made mostly of calcium phosphate that form inside the salivary duct. The submandibular gland is especially prone to stones because its duct runs upward against gravity, and the saliva it produces is thicker and more mineral-rich than saliva from other glands.
The hallmark symptom is swelling that comes and goes with meals. When you start eating, your brain signals the gland to produce saliva. If a stone is blocking the duct, saliva backs up behind it, and the gland balloons painfully. After the meal, the pressure gradually eases and the swelling goes down, only to return the next time you eat. This cyclical pattern of swelling during meals and shrinking between them is a strong signal that a stone is the problem.
Stones range from tiny grains to over a centimeter across. Smaller ones sometimes pass on their own with the right encouragement (more on that below). Larger ones may need to be removed by a specialist using a tiny scope threaded into the duct, or occasionally through a small incision in the floor of the mouth.
Bacterial Infection
When bacteria travel up the salivary duct and into the gland, the result is an infection that causes rapid, painful swelling, redness, warmth over the skin, and sometimes pus draining into the mouth from under the tongue. You may also run a fever. The most common culprit is Staphylococcus aureus, though infections are often caused by a mix of bacteria including streptococci and anaerobes.
Bacterial infections of the submandibular gland tend to strike when saliva flow is already reduced. Dehydration, post-surgical recovery, certain medications (especially antidepressants and antihistamines), and poor oral hygiene all create conditions where bacteria can take hold. A salivary stone that partially blocks the duct can also set the stage for infection, so these two causes sometimes overlap.
Treatment involves antibiotics that target staph bacteria, along with hydration and measures to stimulate saliva flow. Most infections respond well within a few days, but if the gland becomes severely swollen with pus collecting inside it, drainage by a specialist may be necessary.
Viral Causes
Several viruses can inflame the salivary glands, including the submandibular glands. Mumps is the classic example, though it’s far less common in vaccinated populations. Other viruses that can cause salivary gland swelling include Epstein-Barr virus (the cause of mono), parainfluenza viruses, and HIV. Viral swelling tends to affect both sides and often involves the parotid glands (in front of the ears) as well. It typically resolves on its own as the infection clears.
Autoimmune Conditions
Sjögren’s syndrome, an autoimmune condition where the immune system attacks moisture-producing glands, causes submandibular or parotid gland enlargement in about half of affected patients at some point during the disease. The key difference from infectious causes is that the swelling tends to be gradual, recurring, and accompanied by persistent dryness of the eyes and mouth. If you notice that your eyes feel gritty, you rely on eye drops regularly, your mouth is chronically dry, or you need to sip liquids constantly to swallow food, Sjögren’s is worth investigating.
Tumors
Tumors of the submandibular gland are uncommon, but they carry a higher malignancy rate than tumors in other salivary glands. Roughly half of submandibular gland tumors turn out to be malignant. A tumor typically presents as a firm, slowly growing, painless mass rather than the sudden tender swelling of an infection or stone. Warning signs that point toward something more serious include numbness or weakness on one side of the face, a mass that feels fixed to the tissue underneath rather than moveable, and enlarged lymph nodes in the neck.
How Doctors Figure Out the Cause
Your doctor will start with a physical exam, pressing on the gland and the floor of your mouth to feel for stones or masses and checking whether saliva flows from the duct opening. Ultrasound is usually the first imaging test ordered because it’s quick, painless, and good at spotting stones and masses, though it misses some smaller stones located toward the front of the duct. CT scanning is significantly more sensitive, catching about 98% of stones compared to ultrasound’s 65%, so it’s often used when ultrasound comes back normal but suspicion remains high.
If a mass is found and a tumor is suspected, a fine-needle biopsy can help determine whether it’s benign or malignant before any surgery is planned.
What You Can Do at Home
If your swelling follows the classic mealtime pattern suggesting a stone, conservative measures are worth trying before any procedure. The goal is to flush saliva through the duct forcefully enough to dislodge or push out a small stone.
- Warm compresses: Apply a warm, damp cloth to the swollen area for 10 to 15 minutes several times a day. Heat increases blood flow and helps relax the duct.
- Gland massage: Using your fingers, gently but firmly press along the gland from behind your jaw toward the front of your mouth, pushing toward the duct opening under your tongue. This “milking” motion can help move a small stone forward.
- Sour foods and drinks to stimulate saliva: Anything that makes your mouth water creates pressure behind the stone. Research testing various options found that pure lemon juice and malt vinegar were by far the most effective, producing roughly 9 milliliters of saliva per minute. Sour boiled sweets like lemon sherbet also work well. The higher the citric acid content, the stronger the saliva response.
- Stay well hydrated: Drinking plenty of water keeps saliva thin and flowing, reducing the chance of the stone becoming more firmly lodged.
Combining all four, applying heat, massaging, sucking on something sour, and staying hydrated, gives you the best shot at passing a small stone on your own.
Signs That Need Urgent Attention
Most submandibular gland swelling is uncomfortable but not dangerous. However, a few situations require prompt medical attention. Rapidly spreading swelling that extends to both sides of the floor of the mouth and down into the neck can signal Ludwig’s angina, a deep tissue infection that can compromise your airway. It typically comes with fever, fatigue, difficulty opening your mouth, and visible neck swelling. Any facial weakness or numbness on the affected side, a mass that feels anchored in place, or swelling that keeps growing over weeks without responding to treatment all warrant urgent evaluation by a head and neck specialist.