An infected tooth typically shows visible changes in both the tooth itself and the surrounding gum tissue. The tooth may turn gray or dark brown, and the gums nearby often develop a swollen bump that looks like a pimple or boil. These signs can range from subtle discoloration to dramatic swelling that extends into the face, depending on how far the infection has progressed.
Changes to the Tooth Itself
A tooth with an active infection doesn’t always look dramatically different at first glance. Early decay shows up as brown stains or small holes in the enamel. As the infection reaches deeper into the tooth’s inner nerve, the color shifts more noticeably. A tooth with a dead or dying nerve can turn gray, sometimes suddenly. This gray discoloration happens because the blood supply inside the tooth has been cut off, and the tissue is breaking down internally.
You might also notice that the tooth looks slightly different from its neighbors in shape. If decay has been progressing for a while, part of the tooth structure may have broken down, leaving a visible cavity or rough, crumbling edges. In advanced cases, a large portion of the crown (the visible part of the tooth) can be missing entirely, leaving a jagged shell.
What the Gums Look Like
The gums around an infected tooth are often the most obvious visual clue. A dental abscess looks like a boil or pimple on the gum tissue, usually near the base of the affected tooth. This bump is typically darker than the surrounding gum and visibly swollen. The swelling can range from mild, barely noticeable puffiness to a large, tense lump.
Healthy gum tissue is pink and firm. Infected gums turn red, appear puffy, and may bleed easily when touched or brushed. In some cases, the abscess develops an open, draining sore on the side of the gum. When this happens, you may notice a foul taste in your mouth or persistent bad breath. That taste comes from pus draining out of the infection site. Pus is a thick, yellowish-white fluid made up of dead tissue and white blood cells, essentially the debris left behind as your immune system fights the bacteria.
Swelling Beyond the Mouth
When a tooth infection spreads past the gum line, it becomes visible on the outside of the face. Periapical abscesses (infections at the root tip) can cause swelling in the jaw, cheeks, and the floor of the mouth. One side of the face may look noticeably puffier than the other. The skin over the swollen area often feels warm and tight.
Lymph nodes in the neck frequently swell and become tender. You can feel these as firm, sensitive lumps along the side of the neck or under the jaw. Swollen lymph nodes are a sign that your immune system is actively responding to the infection spreading beyond the tooth.
How Infection Progresses Visually
Tooth infections don’t appear overnight. They develop in stages, and each stage has its own visual and physical clues.
In the earliest stage, the nerve inside the tooth becomes inflamed but is still alive. This is called reversible pulpitis. There may be no visible changes at all. Pain comes with hot or cold food and drinks but fades quickly once the trigger is removed. At this point, the tooth and gums can still look completely normal.
If the inflammation worsens, it becomes irreversible. Pain lingers long after temperature changes, strikes spontaneously, and can radiate to nearby teeth so that it’s hard to pinpoint which tooth is the problem. Visually, you may start seeing slight gum redness or swelling near the affected tooth.
Once the nerve dies, bacteria can spread through the root tip into the surrounding bone and soft tissue. This is when the classic abscess bump appears on the gum. The tooth may darken to gray. Facial swelling can develop rapidly from this point, sometimes within hours.
What It Looks Like in Children
Tooth infections in baby teeth follow a similar pattern but can progress faster because primary teeth have thinner enamel and shorter roots. Parents should watch for swollen cheeks, lips, or gums, as this swelling can spread quickly in children. Redness or bleeding gums during brushing suggest infection or advanced decay. Pus around a tooth or along the gum line is a clear sign of active infection.
Children may also develop a mild to moderate fever and swollen lymph nodes near the neck. Because kids can’t always describe dental pain accurately, visible changes in the face and gums are often the first clue parents notice.
What Dentists See on X-Rays
Some of the most important signs of a tooth infection are invisible to the naked eye. On a dental X-ray, an infected tooth shows a dark shadow at the tip of the root. This dark area represents bone that has been destroyed by the infection, creating a pocket where bacteria and pus have collected. A healthy root tip sits snugly in solid bone, so that dark halo is a reliable sign that infection has spread beyond the tooth itself.
X-rays are particularly useful because they can reveal infections before any visible symptoms appear on the gums or face. A tooth that looks fine from the outside can have significant bone destruction underneath.
Warning Signs of a Dangerous Spread
Most tooth infections stay localized, but in rare cases they can spread into the deep tissue spaces of the neck and throat. The most serious form of this, called Ludwig’s angina, causes bilateral swelling under the chin and along the floor of the mouth. The tongue swells and gets pushed upward and backward, which can obstruct the airway.
Visual warning signs of a spreading infection include rapidly increasing swelling that extends down the neck, difficulty swallowing or an inability to swallow saliva, and a visibly swollen or protruding tongue. Audible changes in breathing, like stridor (a high-pitched sound when inhaling), difficulty speaking, and severe dehydration from not being able to swallow are all signals that the infection has become a medical emergency. Fever, rapid heart rate, and feeling generally unwell alongside facial swelling suggest the infection has entered the bloodstream and needs immediate care.
The American Dental Association’s current guidelines emphasize that localized tooth infections are best treated with dental procedures like draining the abscess or performing root canal therapy. Antibiotics are added when the infection shows signs of spreading systemically, including fever or malaise.