An infected tooth typically announces itself with pain that throbs, lingers, or wakes you up at night. But not every toothache means infection, and some infections cause surprisingly little pain at first. The key signs to watch for are pain that sticks around after exposure to hot or cold, swelling in your gums or face, and a foul taste in your mouth. Here’s how to tell what’s happening and when it needs urgent attention.
The Earliest Warning Signs
Tooth infections don’t appear overnight. They usually start with inflammation inside the tooth’s inner tissue, a condition called pulpitis. At this stage, the nerve inside your tooth is irritated but not yet dead. You’ll notice sharp sensitivity to cold drinks or sweet foods, but the sensation disappears within a few seconds. Your tooth feels normal the rest of the time, and tapping on it doesn’t hurt.
The critical shift happens when that sensitivity starts to linger. If a sip of hot coffee or a cold drink triggers a throbbing or aching pain that hangs on for more than a few seconds, the inflammation has likely progressed to the point where the nerve tissue can’t recover on its own. Lingering sensitivity to heat is one of the most reliable signs that things have crossed from “irritated tooth” to “tooth that needs treatment.” At this stage, you might also notice spontaneous pain, meaning it hits without any trigger at all, often at night when you’re lying down.
What a Tooth Infection Feels Like
Once the nerve tissue inside a tooth dies from infection, bacteria can spread beyond the tooth’s root into the surrounding bone and gum tissue. This is when a dental abscess forms. The pain often becomes more constant and harder to ignore. People describe it as deep, throbbing, and radiating into the jaw, ear, or temple on the same side. Biting down on the tooth or even pressing your tongue against it can send a jolt of pain through your jaw.
Some infections cause the tooth to feel slightly “tall” in your mouth, as if it’s sitting higher than the teeth around it. That sensation comes from pressure building at the root tip, which can physically push the tooth upward in its socket. The tooth may also feel loose. Both of these signs point to infection that has moved beyond the tooth itself and into the bone that holds it in place.
Visible Signs in Your Mouth
Not all infected teeth look abnormal from the outside, but many do produce visible changes if you know where to look. The most common is a swollen, red bump on the gum near the affected tooth. This bump, sometimes called a gum boil, is a small pocket of pus that has worked its way to the surface. It can appear as a raised, red-to-yellow spot that bleeds easily when touched and may drain pus on its own.
If the bump ruptures, you’ll likely notice a sudden rush of salty, bitter, or foul-tasting fluid in your mouth. The pain often drops dramatically right after, because the pressure has been released. That relief can be misleading. The infection is still there; it’s just found an exit route. You might also notice persistent bad breath that doesn’t improve with brushing, or a bad taste that comes and goes throughout the day as the abscess continues to drain.
Darkening of a tooth is another clue. A tooth that has turned gray or brown compared to its neighbors may have lost its blood supply due to infection or past trauma. This discoloration doesn’t always mean active infection, but combined with other symptoms, it’s a strong indicator.
Two Types of Tooth Infection
Tooth infections fall into two main categories, and telling them apart helps you understand what’s going on.
A periapical infection starts inside the tooth and spreads out through the root tip. This is the classic “infected tooth” most people picture. It’s usually caused by deep decay, a crack in the tooth, or damage from an old filling that allowed bacteria to reach the nerve. The pain tends to be localized to one specific tooth, and that tooth often won’t respond normally to cold or heat because the nerve inside it has died.
A periodontal infection starts in the gum tissue surrounding the tooth rather than inside it. These are tied to gum disease or sometimes to something as simple as a piece of dental floss or food wedged deep under the gumline. The swelling tends to sit along the side of the tooth rather than at the root tip. The tooth itself usually responds normally to temperature because the nerve inside it is healthy. Instead, you’ll notice gum tenderness, swelling, and sometimes pus oozing from the gum pocket when you press on it. The tooth may feel loose because the infection is destroying the bone and tissue that support it.
Signs the Infection Is Spreading
A tooth infection that stays contained near the tooth is painful but manageable with dental treatment. The danger comes when bacteria enter the bloodstream or spread into surrounding tissues. This transition can happen within weeks or months if an abscess goes untreated, and the signs are distinct from ordinary tooth pain.
Fever is the most straightforward signal that your body is fighting a spreading infection. Swollen, tender lymph nodes under your jaw or along the side of your neck mean your immune system is actively trying to contain bacteria that have moved beyond the tooth. Swelling that extends from your gum into your cheek, under your eye, or along your jaw suggests the infection has entered the soft tissues of your face.
Fatigue and a general feeling of being unwell can accompany these symptoms, and they’re easy to dismiss as unrelated. If you’ve had a nagging toothache for days or weeks and then start feeling run down with a low-grade fever, the connection is worth taking seriously.
When It Becomes an Emergency
Most tooth infections are treated in a dentist’s office on a routine basis. But certain symptoms require emergency care, not a scheduled appointment.
- Swelling that spreads to your neck or under your tongue. This can compress your airway and make it difficult to breathe. It can escalate in hours.
- Difficulty swallowing or opening your mouth. This suggests the infection has moved into deep tissue spaces in your jaw or throat.
- High fever with facial swelling. A combination of fever, rapid heart rate, and visible swelling indicates the infection is systemic.
- Difficulty breathing. Go to an emergency room immediately.
Once a dental infection spreads to the jaw, neck, or deeper structures, it can become life-threatening within days. Abscesses from tooth decay can take months to develop in the first place, so there’s usually a long window to get treatment. But once the infection crosses into surrounding tissues, the timeline accelerates sharply.
What Happens at the Dentist
If you suspect an infected tooth, a dentist can confirm it quickly. They’ll tap on your teeth to see which one reproduces the pain, apply cold or heat to test whether the nerve inside is still alive, and take an X-ray to look for dark areas around the root tips that indicate bone loss from infection. If the infection appears to have spread into your neck or face, a CT scan can show exactly how far it’s gone.
Treatment depends on how advanced the infection is. A tooth with a dying nerve but no abscess may need a root canal to remove the infected tissue and save the tooth. If an abscess has formed, draining the pus and prescribing antibiotics is usually the first step, followed by either a root canal or extraction. Periodontal infections often require deep cleaning of the gum pockets along with antibiotics. In most cases, the pain improves significantly within a day or two of treatment, though full healing takes longer.
The one thing that won’t work is waiting it out. Tooth infections don’t resolve on their own. The pain might fade temporarily if an abscess drains or if the nerve dies completely, but the bacteria remain active and the infection continues to spread slowly through the bone. A tooth that suddenly stops hurting after weeks of pain isn’t healing. It’s progressing.