Pain in the back of your mouth when you eat usually comes from one of a handful of common causes: an emerging wisdom tooth, a canker sore, inflamed tonsils, a salivary gland stone, or a jaw joint problem. The location and timing of the pain narrow it down. Some of these resolve on their own in days, while others need professional treatment.
Wisdom Teeth and Gum Flaps
If the pain is deep in the back corner of your jaw, a partially erupted wisdom tooth is one of the most likely culprits. When a wisdom tooth only breaks partway through the gum, it leaves a flap of tissue that traps food particles and bacteria. That flap becomes swollen and tender, and every time you bite down, your upper teeth press directly into the inflamed tissue. This condition, called pericoronitis, is extremely common in people between 17 and 25 but can happen later.
The pain tends to be worst on one side, and you may notice a bad taste or smell from bacteria collecting under the flap. In mild cases, keeping the area clean can settle things down. But pericoronitis often recurs until the wisdom tooth is removed. If the upper wisdom tooth is also biting into the swollen lower gum, a dentist may recommend removing both.
Canker Sores and Soft Tissue Irritation
A canker sore (aphthous ulcer) on the soft palate, the back of the tongue, or near the tonsils can make eating genuinely miserable. These small ulcers sting on contact with food, especially anything acidic, salty, or spicy. Citrus fruits, tomatoes, strawberries, fizzy drinks, and alcohol all lower the pH inside your mouth, which disrupts the protective lining and worsens the pain. Even the physical act of chewing something crunchy or sharp, like crusty bread or chips, can aggravate the sore.
Most canker sores heal within one to two weeks without treatment. While you wait, softer foods at mild temperatures are easiest to tolerate. A warm saltwater rinse (one and a half teaspoons of salt dissolved in eight ounces of warm water) can help draw fluid out of swollen tissue through osmosis, reducing discomfort. If you’re getting canker sores frequently or they’re unusually large, that’s worth mentioning to a dentist or doctor.
Tonsillitis and Throat Infections
When the pain is centered at the very back of your mouth and gets worse with swallowing rather than chewing, your tonsils or throat lining may be inflamed. Tonsillitis causes redness, swelling, and sometimes visible white patches on the tonsils. Pharyngitis (inflammation of the throat itself) produces similar swallowing pain but may feel more diffuse. You can have both at once.
Viral infections are the most common cause and typically clear up on their own. Bacterial infections, particularly strep, need antibiotic treatment. A few warning signs point to something more serious: increasing pain with every swallow, visible swelling on one side of the throat (which could indicate an abscess forming around the tonsil), drooling or difficulty swallowing your own saliva, or any trouble breathing. These need prompt medical attention.
Salivary Gland Stones
This is one people rarely think of, but it has a very distinctive pattern. Salivary gland stones are mineral deposits that block the ducts carrying saliva into your mouth. The largest salivary glands sit just below and behind your jaw on each side. When a stone blocks the duct, saliva backs up behind it every time your body ramps up production, which happens the moment you start eating or even see food.
The hallmark symptom is sudden, intense pain and swelling near the back of your jaw that appears at the start of a meal and fades within an hour or two afterward. A pea-sized stone can cause significant discomfort. If you notice this meal-triggered pattern of swelling that comes and goes, a salivary stone is a strong possibility. Small stones sometimes pass on their own; larger ones may need to be removed.
Jaw Joint Problems
Temporomandibular disorders (often called TMJ or TMD) involve the joint connecting your lower jaw to your skull, located just in front of each ear. Problems here cause pain in the chewing muscles and the joint itself, and that pain often radiates into the back of the mouth, the face, and the neck. It tends to worsen with prolonged chewing, hard foods, or wide mouth opening.
You might also notice clicking or popping when you open your jaw, stiffness in the morning, or a feeling that your bite is slightly off. TMD encompasses over 30 different conditions, so the treatment depends on the specific issue. Many cases improve with softer foods, jaw rest, gentle stretching, and over-the-counter pain relief.
Less Common Causes
Glossopharyngeal neuralgia is a rare nerve condition that causes sudden, sharp, electric-shock-like pain near the tonsils or the back of the tongue. It’s triggered by swallowing, chewing, talking, or coughing. The pain typically lasts seconds to a couple of minutes and can radiate to the ear. It’s uncommon enough that doctors need imaging and specific nerve tests to confirm it, but it’s worth knowing about if your pain is severe, brief, and shock-like in quality.
Eagle syndrome is even rarer, affecting roughly 0.16% of the population. It involves an abnormally long bony projection deep in the neck that presses on nerves or blood vessels. It can cause pain near the tonsils or back of the tongue that worsens when you chew, yawn, or turn your head, along with a persistent feeling of something stuck in your throat.
What to Look for in the Mirror
Grab a flashlight and a mirror and open wide. Healthy tissue inside your mouth should be uniformly pink and smooth. Anything that looks different is a clue: redness, white patches, swelling, a visible ulcer, a pimple-like bump on the gum, or a flap of tissue partially covering a back molar. Swelling concentrated under the jaw or on one side of the throat is also informative.
A few signs suggest you shouldn’t wait to get professional help: fever and chills alongside the mouth pain (your body is fighting a significant infection), visible facial swelling on one side, pus or a foul taste coming from the area, a tooth that feels loose, or pain that’s been steadily intensifying over several days. Throbbing pain that won’t let up often points to an abscess, an exposed nerve, or a deep cavity, all of which need treatment rather than time.