The most common symptom of a tooth infection is a persistent, throbbing pain that can range from mild to severe. But tooth infections produce a surprisingly wide range of symptoms beyond the toothache itself, including swelling, sensitivity to temperature, swollen lymph nodes, and sometimes fever. Recognizing these signs early matters because untreated dental infections can spread to surrounding tissues and, in rare cases, become dangerous.
Pain: The First and Most Obvious Sign
Tooth infection pain typically starts as a sharp sensation triggered by chewing or biting down. In the early stages, the nerve inside the tooth (the pulp) is inflamed but not yet permanently damaged. At this point, pain tends to come and go, flaring up when you eat something hot, cold, or sweet, then fading within seconds.
As the infection progresses and the nerve damage becomes irreversible, the pain changes character. It shifts from brief, sharp jolts to a deep, throbbing ache that can last for hours or become constant. Many people notice it intensifies when they lie down at night, because the change in position increases blood flow to the head. The pain can also radiate along the jaw, up toward the ear, or into the temple on the same side, making it difficult to pinpoint exactly which tooth is the source.
Swelling and Visible Changes
When a tooth infection forms an abscess (a pocket of pus), swelling is one of the clearest visual signs. Where the swelling appears depends on which tooth is infected. An upper tooth infection often causes swelling in the cheek or below the eye, while a lower tooth infection tends to swell along the jawline or under the chin.
You may also notice a small, pimple-like bump on the gum near the affected tooth. This is called a fistula or a “gum boil,” and it forms when the infection creates a drainage channel through the bone and gum tissue. If this bump ruptures on its own, you’ll suddenly taste a rush of salty, foul-tasting fluid in your mouth. That fluid is pus. While the pressure relief often reduces pain temporarily, the underlying infection is still present and still needs treatment.
The gums around the infected tooth frequently appear red, swollen, or puffy compared to the surrounding tissue. In some cases, the tooth itself may look darker than its neighbors, which can signal that the nerve inside has died.
Sensitivity to Hot and Cold
Temperature sensitivity is one of the earlier warning signs that something is wrong inside a tooth. In mild cases, you’ll feel a quick zing when drinking ice water or sipping hot coffee, but the sensation disappears almost immediately once the trigger is removed. This type of sensitivity can sometimes be reversed with treatment.
When the infection is more advanced, the sensitivity becomes prolonged and intense. Cold or hot foods trigger pain that lingers for 30 seconds or more after the stimulus is gone. At this stage, the nerve is typically damaged beyond repair. Some people also notice that the tooth becomes painful under any pressure, even the light tap of a tongue.
Taste, Smell, and Other Sensory Symptoms
A persistent bad taste in the mouth is a telltale sign of a dental infection, especially when an abscess is actively draining. The taste is often described as metallic, bitter, or salty. Along with it, you or people close to you may notice foul-smelling breath that doesn’t improve with brushing or mouthwash. These sensory changes come from the bacteria and pus associated with the infection, and they tend to be most noticeable in the morning or after periods of not eating or drinking.
Swollen Lymph Nodes and Fever
Your body responds to a tooth infection the same way it responds to infections elsewhere: by activating the immune system. The lymph nodes under your jaw and along your neck often swell and become tender to the touch. You can feel them as firm, marble-sized lumps that are sore when you press on them or turn your head.
Fever is another systemic sign that the infection is provoking an immune response. Not every tooth infection causes a fever, but when one does appear, it signals that the body is fighting harder to contain the spread. General fatigue and feeling unwell often accompany the fever. If you develop a high fever alongside dental pain, that’s a sign the infection may be spreading beyond the tooth itself.
Symptoms in Children
Children with tooth infections experience many of the same symptoms as adults, but they often can’t describe what they’re feeling. Boston Children’s Hospital lists the key signs to watch for: toothache, fever, cheek swelling, sensitivity to hot or cold or pressure, swollen lymph nodes, and redness or swelling of the gums next to a tooth. Younger children may refuse to eat, become unusually irritable, or wake up crying at night. If an abscess ruptures in a child’s mouth, they may spit out or swallow bad-tasting fluid without understanding what it is.
Difficulty Opening Your Mouth
Some tooth infections, particularly those involving the back molars, cause a condition called trismus, where the jaw muscles tighten and you can’t fully open your mouth. This happens when the infection spreads into the tissues and muscles surrounding the jaw. If you find yourself unable to open wide enough to fit two fingers between your teeth, that’s a significant sign. A study of 499 patients with severe dental infections found that limited mouth opening was associated with more complicated cases that were harder to manage.
Warning Signs of a Spreading Infection
Most tooth infections stay localized and are resolved with dental treatment. But in rare cases, the infection can spread into the deep tissues of the neck and floor of the mouth, creating a potentially life-threatening situation. The most serious of these complications is Ludwig’s angina, a rapidly spreading infection that causes the neck to swell dramatically and the tongue to push forward and upward, which can block the airway.
The symptoms of a spreading dental infection include severe neck swelling or discoloration, a protruding or swollen tongue, difficulty swallowing, changes in your voice (sounding muffled or hoarse), drooling because you can’t swallow saliva, and trouble breathing. These symptoms can develop suddenly. High fever, rapid heart rate, and confusion are additional red flags that the infection has entered the bloodstream.
These severe complications are uncommon, but they escalate quickly. Difficulty breathing or swallowing alongside dental pain warrants an immediate trip to the emergency room, not a dental office.
How Symptoms Change Over Time
Tooth infections don’t stay static. In the early phase, you might notice only occasional sensitivity or mild discomfort when eating. Over days to weeks, the pain becomes more constant and intense as the infection reaches the nerve. Once an abscess forms, swelling and throbbing pain typically peak. Some people experience a sudden relief of pain when the abscess drains on its own or when the nerve fully dies, and they mistakenly believe the problem has resolved. It hasn’t. The infection is still present in the bone and surrounding tissue, and without treatment it will continue to cause damage and can flare up again, often worse than before.
The progression isn’t always predictable. Some infections smolder at a low level for months, producing only mild symptoms like occasional tenderness or a small gum bump. Others escalate within days to significant swelling and fever. The speed depends on the type of bacteria involved, the location of the tooth, and how well your immune system is functioning.