A tooth infection typically shows up as a swollen, pimple-like bump on the gum near the affected tooth, often darker in color than the surrounding tissue. In some cases, the bump drains yellowish-white pus when pressed or on its own. But the visible signs extend well beyond that single bump, and some of the most important signals aren’t in your mouth at all.
The Gum Boil: The Most Obvious Sign
The hallmark of a tooth infection is what dentists call a gum boil or abscess. It looks like a small, raised pimple sitting on your gum line, usually right next to the problem tooth. The bump is typically darker than the rest of your gum tissue, ranging from deep red to purplish, and it may look shiny or stretched tight from the pressure of pus building underneath.
The swelling can range from mild (a small, barely noticeable bump) to severe (a visibly distended area that changes the shape of your gum or even your face from the outside). Some gum boils develop a white or yellowish head, much like a skin pimple, which is pus collecting near the surface. If the boil ruptures on its own, you’ll notice a sudden foul taste in your mouth as the pus drains. This temporarily relieves pressure and pain, but the infection is still active underneath.
Changes to Gum Color and Texture
Even without a distinct bump, infected gum tissue looks noticeably different from healthy tissue. Healthy gums are pale pink, firm, and stippled (a slight orange-peel texture). Infected gums turn red, swollen, and smooth or shiny. They may feel spongy or tender when you press on them, and they bleed easily during brushing or flossing.
As the infection progresses, the gums can start pulling away from the tooth, making the tooth look longer than its neighbors. This recession creates deeper pockets between the tooth and gum. In a healthy mouth, these pockets measure 1 to 3 millimeters. Infection can deepen them significantly, giving bacteria more space to thrive where your toothbrush can’t reach.
What the Tooth Itself Looks Like
The infected tooth may have visible damage: a dark cavity, a crack, or a large area of discoloration. Sometimes the tooth appears grey or brownish compared to surrounding teeth, which can signal that the nerve inside has died. You might also notice the tooth seems slightly loose or sits at a different angle than before, because the infection is eroding the bone and tissue anchoring it in place.
Not every infected tooth has visible surface damage, though. Infections that start at the root tip (often from an old filling or trauma) can look completely normal from the outside. These are the ones that typically show up only on dental X-rays, where they appear as a dark shadow at the tip of the root, indicating bone loss from the infection spreading.
Signs Outside Your Mouth
A tooth infection doesn’t always stay contained to the gum line. One of the most common external signs is facial swelling on the side of the affected tooth. Your cheek, jaw, or the area under your chin may look puffy or feel warm to the touch. In some cases, the swelling is dramatic enough that one side of your face looks visibly larger than the other.
Swollen lymph nodes are another telltale sign. The nodes under your chin and along the sides of your neck often enlarge and become tender when your body is fighting a dental infection. They feel like firm, marble-sized lumps just beneath the skin. A low-grade fever, a persistent bitter taste, and bad breath that doesn’t improve with brushing round out the typical picture.
What a Dangerous Spread Looks Like
Most tooth infections stay localized and respond well to treatment. But in rare cases, the infection spreads to deeper tissues, and recognizing this early matters enormously.
One serious complication is a fast-moving infection of the floor of the mouth called Ludwig’s angina. It causes swelling underneath the jaw and the front of the neck that comes on suddenly and progresses quickly. The tongue may push forward or swell, and the skin over the neck can become discolored. The critical danger is airway obstruction: difficulty breathing, difficulty swallowing, drooling, and slurred speech are all warning signs. This is a medical emergency requiring immediate care, because without treatment it can block the airway entirely.
If the infection enters the bloodstream, the signs shift from local to whole-body. A high or spiking fever, chills, a rapid heart rate, dizziness, nausea, and extreme fatigue suggest the infection has gone systemic. These symptoms call for emergency medical attention, not a dental appointment.
What Your Dentist Sees That You Can’t
Much of a tooth infection is invisible to the naked eye, which is why dental X-rays are a standard part of diagnosis. On an X-ray, an abscess at the root tip appears as a dark halo around the end of the tooth root, representing bone that the infection has dissolved. X-rays also reveal bone loss between teeth, hidden cavities that served as the infection’s entry point, and the extent of damage below the gum line.
Your dentist will also probe the pockets around each tooth with a small measuring instrument. Pockets deeper than 3 millimeters, combined with bleeding and tenderness, confirm active infection even when the surface looks relatively normal. This is why a tooth infection can be well established before you notice anything visually wrong on your own. By the time a gum boil forms or your face swells, the infection has usually been building for days or weeks underneath.