An infected tooth typically announces itself with pain that throbs or pulses on its own, especially at night, and gets worse when you bite down or drink something hot. If you’re noticing a combination of persistent tooth pain, swelling in your gums, and a bad taste in your mouth, there’s a good chance infection is involved. Here’s how to tell what’s going on and what to do about it.
Pain Patterns That Point to Infection
Not all tooth pain means infection. A cracked tooth or a cavity can hurt without any bacteria being involved. The difference is in how the pain behaves. Infected teeth tend to produce a deep, throbbing ache that persists even when you’re not eating or drinking. It often gets worse when you lie down, which is why many people first notice it at bedtime. The pain can radiate into your jaw, ear, or temple on the same side of your face.
Temperature is another reliable clue. Early in an infection, the tooth may be extremely sensitive to hot or cold drinks, with pain that lingers for several seconds after you remove the stimulus. A healthy tooth might zing briefly when it hits something cold, but the sensation fades almost immediately. When pain from heat or cold hangs around for more than a few seconds, or when hot liquids in particular trigger intense, lingering pain, the nerve inside the tooth is likely inflamed or dying.
As infection progresses and the nerve tissue dies, the tooth may actually stop responding to temperature altogether. At that point, the dominant symptom shifts: biting pressure or even light tapping on the tooth produces a sharp, localized ache. If tapping on a specific tooth with a fingernail or the handle of a toothbrush reliably reproduces the pain, that’s a strong indicator of infection at the root tip.
What to Look for in the Mirror
Pull your lip or cheek away from the sore area and look at the gum tissue around the tooth. A healthy gum line is pale pink and firm. Infected gums often look red, puffy, or shiny with swelling. The most telltale visual sign is a small bump on the gum near the root of the tooth, sometimes called a gum boil. It looks like a pimple and may be white, yellow, or red. This bump is a drainage point for pus collecting at the root tip.
If that bump bursts on its own, you’ll get a sudden rush of foul-smelling, salty fluid in your mouth. Oddly, you may also feel temporary pain relief, because the pressure that built up around the root has been released. That relief doesn’t mean the infection is gone. It means the abscess found an exit route, and the underlying problem remains.
Swelling can also extend beyond the gum line. A puffy cheek, swollen jaw, or visible asymmetry in your face suggests the infection has spread into the surrounding soft tissue. In some cases, the swelling can make it difficult to fully open your mouth or swallow comfortably.
Taste, Smell, and Other Sensory Clues
A persistent bad taste that doesn’t go away with brushing is a common early sign. This happens when pus slowly leaks from the infection site into your mouth. The taste is often described as metallic, sour, or bitter. You might also notice bad breath that seems to come from a specific area rather than your mouth in general. If other people can smell it, or if you notice the odor even after thorough brushing, that’s worth paying attention to.
Signs the Infection Is Spreading
A tooth infection that stays localized around the root tip is painful but manageable with dental treatment. The situation becomes more serious when infection moves into surrounding tissues or enters the bloodstream. Watch for these warning signs:
- Fever: A temperature above 100.4°F (38°C) alongside tooth pain suggests your body is fighting a spreading infection.
- Swollen lymph nodes: Feel along the underside of your jaw and down the front of your neck. Tender, swollen lumps in these areas mean your immune system is actively responding to nearby infection.
- Facial swelling that worsens quickly: Swelling that progresses over hours, especially if it moves toward your eye or down into your neck, needs immediate attention.
- Difficulty breathing or swallowing: Infection spreading into the floor of the mouth or throat tissues can compromise your airway. This is a medical emergency.
- General malaise: Feeling unusually fatigued, achy, or unwell alongside dental symptoms indicates the infection is affecting your whole body.
A rare but serious complication called Ludwig’s angina occurs when infection spreads rapidly into the tissues beneath the tongue and in the neck, causing severe swelling that can obstruct breathing. Another uncommon but dangerous possibility is infection tracking upward through facial veins toward the brain, causing a condition called cavernous sinus thrombosis. Both are reasons why spreading dental infections shouldn’t be managed with a “wait and see” approach.
Simple Checks You Can Do at Home
You can’t diagnose a tooth infection with certainty on your own, but a few simple tests can help you figure out whether to make a dental appointment or head to urgent care.
The tap test is the simplest. Using the end of a spoon or your fingernail, gently tap on the biting surface of the tooth you suspect. Then tap on the tooth next to it for comparison. If the suspect tooth produces noticeably more pain or a sharp zing, infection at the root is likely. You can also try biting down on something firm, like a cotton roll or a folded piece of cloth. Pain that spikes with biting pressure and then lingers after you release points toward infection around the root.
Check for swelling by running your finger along the gum tissue on both the cheek side and the tongue side of the tooth. Compare it to the same spot on the opposite side of your mouth. Puffiness, tenderness, or a distinct bump on one side confirms localized swelling. Finally, feel for swollen lymph nodes by pressing gently under the angle of your jaw on the affected side. A tender, marble-sized lump that isn’t present on the other side is a sign your body is responding to infection nearby.
What Happens at the Dentist
A dentist confirms a tooth infection using a few quick tests. The most common is a cold test, where a chilled instrument or a cold spray is applied to the tooth. A healthy nerve responds briefly and the sensation fades. An inflamed nerve produces intense, lingering pain. A dead nerve won’t respond at all, which also indicates infection since the nerve tissue has died from bacterial damage.
An electric pulp tester delivers a mild electrical current to the tooth surface to check whether the nerve inside is still alive. You’ll feel a tingling sensation that gradually increases. If you feel nothing at all, the nerve is likely dead. The dentist will also tap on the tooth and press on the surrounding gum to check for tenderness.
An X-ray is usually the deciding piece of evidence. Infection at the root tip shows up as a dark shadow around the end of the root, indicating bone loss caused by the abscess. The X-ray also reveals how extensive the decay is and whether the infection has affected neighboring teeth or the jawbone.
How Tooth Infections Are Treated
The most important thing to know about treatment is that antibiotics alone don’t fix tooth infections. American Dental Association guidelines are clear on this point: for most dental infections in otherwise healthy adults, the recommended treatment is addressing the source directly rather than prescribing antibiotics. That means either a root canal to remove the infected nerve tissue, or an extraction if the tooth can’t be saved. If there’s an abscess, the dentist may drain it to relieve pressure.
Antibiotics are reserved for cases where the infection has spread beyond the tooth into surrounding tissues, or where there are systemic signs like fever and facial swelling. This is because antibiotics can’t penetrate well into the dead tissue inside an infected tooth. They can help control infection that has escaped into living tissue, but they won’t eliminate the bacterial source inside the tooth itself.
For pain management before you can get to a dentist, over-the-counter options work well. Ibuprofen reduces both pain and inflammation, and alternating it with acetaminophen provides stronger relief than either one alone. Rinsing gently with warm salt water several times a day can help draw out superficial pus and soothe irritated gum tissue. Avoid applying heat to the outside of your face, as this can draw infection toward the skin surface and worsen swelling.
Why Timing Matters
Tooth infections don’t resolve on their own. The pain may come and go, sometimes disappearing for days or weeks, but this usually means the infection has found a drainage path or the nerve has died, not that the problem is gone. An infection that goes quiet is still destroying bone around the root tip and can flare up again without warning, often at a worse stage than before.
Getting treatment early also preserves your options. A tooth caught at the early stage of infection can often be saved with a root canal. The same tooth left untreated for months may lose so much supporting bone that extraction becomes the only choice. If you’re noticing any combination of the symptoms described above, particularly throbbing pain, gum swelling, or a bad taste that won’t go away, getting evaluated sooner rather than later gives you the best outcome.