The most common signs of a tooth infection are a persistent, throbbing toothache, swelling in the gum or face, and sensitivity to hot or cold temperatures. These symptoms can start mild and escalate over days or weeks, so recognizing them early makes a real difference in how simple treatment will be.
Pain That Doesn’t Let Up
The hallmark of a tooth infection is a deep, throbbing pain that persists even when you’re not eating or drinking. Unlike a cavity, which typically hurts only when something touches it, infection pain can radiate into your jaw, ear, or neck on the same side. It often intensifies when you lie down, because the change in blood flow increases pressure around the infected area. Many people describe it as a pulsing ache that wakes them up at night.
You may also notice sharp pain when biting down or pressing on the tooth. This happens because infection at the root tip creates inflammation in the surrounding bone, so any pressure on the tooth pushes it into already-irritated tissue. A tooth that suddenly feels “taller” than the others, or that you instinctively avoid chewing on, is worth paying attention to.
Swelling in the Gum, Face, or Neck
Swelling is one of the most visible signs that an infection has moved beyond the tooth itself. It can show up in several ways depending on where the infection is draining.
A small, pimple-like bump on the gum near the affected tooth is called a gum boil. This forms when pus from the infection works its way through the bone and creates a drainage point on the gum tissue, usually along the gum line where the tissue is thinnest. It may pop on its own, releasing a salty or foul-tasting fluid into your mouth, then refill over days. A gum boil that comes and goes is not a sign the infection is healing. It means the infection is still active and has simply found an outlet.
More concerning is swelling in the cheek, under the jaw, or along the neck. This indicates the infection is spreading into the soft tissues of the face. The skin over the swollen area may feel warm and firm to the touch, and opening your mouth fully can become difficult or painful.
Sensitivity to Temperature
An infected tooth often reacts strongly to hot and cold foods or drinks. What sets infection apart from ordinary sensitivity is that the pain lingers. With a healthy but sensitive tooth, a sip of ice water causes a quick zing that fades within a few seconds. With an infected tooth, that pain can hang around for 30 seconds or longer after the stimulus is gone.
In some cases, a tooth that was previously sensitive to cold stops responding entirely. This can actually be a bad sign. It suggests the nerve inside the tooth has died from the infection, which doesn’t mean the problem is over. The infection continues in the bone and tissue around the root even after the nerve is gone, and the lack of cold sensitivity can create a false sense that things are improving.
Bad Taste and Persistent Bad Breath
A foul or bitter taste in your mouth, especially one that seems to come from a specific area, is a strong clue that infection is present. This happens when pus drains from the infection site into the mouth, either through a gum boil or along the edge of a damaged tooth. The bacteria involved in dental infections produce sulfur compounds as they break down tissue, which creates a distinctly unpleasant odor that brushing and mouthwash won’t fully eliminate.
If people around you notice your breath even after good oral hygiene, or if you’re getting a persistent metallic or rotten taste that you can’t trace to anything you ate, that warrants a closer look.
Fever, Fatigue, and Swollen Lymph Nodes
When a tooth infection triggers symptoms beyond your mouth, it means your immune system is fighting harder. A low-grade fever, general fatigue, and a feeling of being unwell can all accompany a dental abscess. You may notice tender, swollen lumps under your jaw or along the side of your neck. These are lymph nodes responding to the infection.
These systemic symptoms don’t always appear. Some people have a significant infection with no fever at all. But when they do show up alongside tooth pain or facial swelling, they confirm that the infection isn’t something your body will resolve on its own.
Sinus Pressure vs. Tooth Infection
Upper tooth infections are easy to confuse with sinus problems, and vice versa. The roots of your upper back teeth sit very close to your sinus cavities, and in some people they actually extend into them. This means a sinus infection can cause aching in several upper teeth at once, mimicking a dental problem. Conversely, an infection in an upper molar can push into the sinus floor and cause congestion, pressure under the eyes, or a runny nose on one side.
The key difference: sinus-related tooth pain usually affects multiple teeth and gets worse when you bend forward or lie down. A true tooth infection typically centers on one tooth, and tapping on that specific tooth reproduces the pain sharply. If you’re unsure which you’re dealing with, a dental exam is the fastest way to sort it out, since an X-ray can reveal infection at the root tip that wouldn’t show up on a sinus evaluation.
Signs the Infection Is Spreading
Most tooth infections stay localized and are treatable with routine dental care. But in rare cases, the infection can spread into deeper spaces of the jaw, throat, or neck. The warning signs of this are hard to miss:
- Difficulty swallowing or breathing: Swelling in the floor of the mouth or throat can narrow your airway. This is a medical emergency.
- Inability to open your mouth: When infection spreads into the muscles used for chewing, your jaw can lock down to a narrow opening.
- Swelling that moves below the jawline: A firm, spreading swelling under the chin or down the neck suggests the infection is tracking into tissue spaces that connect to the chest.
- High fever with facial swelling: A temperature above 101°F (38.3°C) combined with visible facial swelling means the infection is overwhelming your body’s local defenses.
Any of these signs call for an emergency room visit, not a scheduled dental appointment. Infections that reach the throat or neck can compromise breathing quickly and require hospital-level treatment.
What Happens at a Dental Visit
Your dentist will tap on the suspect tooth, apply cold to it, and take an X-ray to look for a dark shadow at the root tip, which indicates bone loss from infection. The tapping test is straightforward: if pressing or lightly tapping the tooth reproduces your pain, inflammation is present around the root. The cold test checks whether the nerve inside the tooth is still alive. A tooth that doesn’t respond to cold at all has likely lost its nerve to infection.
These tests are quick and give your dentist a clear picture of whether infection is present and how far it has progressed. From there, treatment usually involves draining the infection and addressing the source, whether that’s a root canal to save the tooth or an extraction if the damage is too extensive. Antibiotics alone won’t cure a tooth infection because the medication can’t penetrate well into the dead tissue inside the tooth. They’re used as a support measure, not a standalone fix.