An infected tooth typically announces itself with a persistent, throbbing pain that doesn’t fade on its own and often spreads into the jaw, neck, or ear. But pain isn’t the only signal. Swelling, sensitivity changes, bad taste in your mouth, and even fever can all point to an active infection. Knowing which signs matter most helps you gauge how serious the situation is and how quickly you need to act.
The Pain Feels Different From a Normal Toothache
Tooth infection pain is usually constant and throbbing, not the brief zing you get from biting into something cold. It tends to build over hours or days rather than come and go. Many people notice it radiating beyond the tooth itself, traveling along the jawbone, up toward the ear, or down into the neck. Lying down often makes it worse because blood flow to the head increases in that position.
One useful way to tell what’s going on is how your tooth responds to temperature. A tooth that’s just irritated (a condition called reversible pulpitis) will give you a quick, sharp jolt when it hits something cold or sweet, but that pain disappears within a few seconds. An infected tooth behaves differently: sensitivity to heat, cold, or sweets lingers well beyond a few seconds, and the pain may feel like a deep ache or throb rather than a sharp flash. If the nerve inside the tooth has already died, you might lose sensitivity to temperature altogether, yet still feel a dull pain or soreness when you press on the tooth or bite down.
Visible Signs Inside Your Mouth
Look in a mirror with good lighting. An infected tooth may appear darker or discolored compared to the teeth around it. You might see visible breaks, chips, or dark spots in the enamel. The gum tissue around the tooth is often red, puffy, and tender to the touch.
One of the clearest visual signs is a small bump on the gum near the base of the tooth, sometimes called a gum boil. This pimple-like bump is a pocket of pus trying to drain. If it ruptures, you’ll notice a sudden foul taste in your mouth and sometimes temporary pain relief as the pressure drops. Pus can also ooze from around the gumline when you press on the area. A persistent bad taste or bad breath that doesn’t improve with brushing often accompanies active drainage.
Two Types of Tooth Infections
Not all tooth infections start the same way, and recognizing the difference can help you describe your symptoms more clearly.
Periapical Abscess
This type starts at the tip of the root, deep inside the tooth. It usually develops when a cavity, crack, or old filling allows bacteria to reach the soft tissue (pulp) inside the tooth. The nerve eventually dies, and infection builds at the root tip. You’ll typically feel deep, aching pain and won’t get a normal response to hot or cold because the nerve is compromised. A dentist may see a dark shadow at the root tip on an X-ray.
Periodontal Abscess
This type forms in the gum tissue alongside the tooth, usually when a deep gum pocket gets blocked and bacteria become trapped. The most common complaint is a visible swelling on the gum, with or without pain. Biting often makes it worse, and the tooth may feel loose or like it’s sitting slightly higher than the others. Pressing on the swelling can produce pus, and gum probing reveals a deep pocket, often greater than 6 millimeters. Unlike a periapical abscess, the nerve inside the tooth is usually still alive, so the tooth still responds normally to hot and cold.
How Infection Progresses
Dental infections follow a fairly predictable timeline when left untreated. In the first one to three days, you’ll notice a soft, mildly tender swelling. By days two through five, that swelling becomes hard, red, and significantly more painful. Between days five and seven, a true abscess forms, with a defined pocket of pus that may or may not drain on its own.
This timeline isn’t a guarantee that things will stay manageable. Once an abscess forms, the infection can spread into the surrounding bone, into the deep tissue spaces of the face and neck, or into the bloodstream. That progression from a localized pocket of pus to a systemic, life-threatening problem can happen quickly.
Signs the Infection Has Spread Beyond the Tooth
A tooth infection that stays localized is painful but manageable with dental treatment. An infection that spreads systemically is a different situation entirely. Watch for these warning signs:
- Fever: Any temperature above 37.3°C (about 99.1°F) suggests your body is fighting a spreading infection. Higher fevers, especially with chills, signal more serious involvement.
- Swollen lymph nodes: Tender lumps under your jaw or along the sides of your neck indicate your immune system is responding to infection beyond the tooth.
- Facial or neck swelling: Swelling that extends beyond the gum into the cheek, under the jaw, or down the neck means the infection has moved into deeper tissue spaces.
- General malaise: Fatigue, body aches, and an overall feeling of being unwell suggest the infection is affecting your whole system. Dehydration often accompanies this stage.
The most dangerous scenario is when infection spreads into the floor of the mouth and neck, a condition called Ludwig’s angina. This causes severe swelling under the tongue and jaw that can push the tongue upward, making it difficult or impossible to swallow or breathe. If you experience difficulty breathing, difficulty swallowing, or rapidly worsening swelling around your neck, that’s a 911 situation.
Simple Tests You Can Do at Home
These aren’t replacements for a dental exam, but they can help you assess what’s happening before your appointment.
The tap test. Gently tap the suspicious tooth with the handle of a spoon or your fingernail. A tooth with early irritation won’t hurt when tapped. An infected tooth, especially one with a dying or dead nerve, will produce a noticeable ache or sharp pain on contact.
The bite test. Bite down gently on the tooth. Pain on biting, particularly a sensation that the tooth is being pushed upward in its socket, suggests either a periapical infection at the root tip or a periodontal abscess along the gum. If the tooth feels loose, that’s an additional red flag.
The temperature test. Hold a sip of warm (not scalding) water in your mouth near the tooth, then try cold water. If warmth triggers lingering pain, that’s a classic sign of an infected or dying nerve. If neither temperature produces any sensation at all in a tooth that used to be sensitive, the nerve may already be dead, which doesn’t mean the infection is gone. It means the infection has progressed.
The visual check. Pull your lip or cheek away and look at the gum around the tooth. Redness, swelling, a visible bump, or any discharge of pus confirms that infection is present and active.
What Happens at the Dentist
A dentist confirms infection through a combination of clinical tests and imaging. They’ll tap on individual teeth to locate the source of pain, use cold or electrical stimulation to check whether the nerve is still alive, and probe the gum pockets to measure their depth. X-rays or, in more complex cases, 3D cone-beam imaging can reveal bone loss at the root tip, fractures, or the extent of infection spread. Standard X-rays have limitations: they can miss cracks, and metal fillings or crowns sometimes obscure the view. That’s why the clinical exam and your description of symptoms matter as much as the images.
Treatment depends on what the tests reveal. A periapical abscess typically requires either a root canal or extraction. A periodontal abscess needs drainage and deep cleaning of the infected gum pocket. In both cases, antibiotics may be prescribed if there’s evidence the infection has spread beyond the immediate area. The goal is always to remove the source of infection, not just manage the pain, because antibiotics alone won’t resolve a dental abscess permanently. The bacteria have a protected space inside the tooth or gum pocket where medication can’t fully reach.