A tooth abscess typically appears as a swollen, red bump on the gum that resembles a pimple or boil, often with a visible collection of yellowish pus at its center. Depending on the type and severity, the visual signs can range from a small soft spot on the gum near a tooth root to dramatic swelling across the jaw, cheek, or neck.
The Gum “Pimple” or Boil
The most recognizable sign of a tooth abscess is a raised bump on the gum, sometimes called a gum boil. It appears as a smooth, sometimes lobulated (slightly lumpy) growth on the gum tissue. The color ranges from yellow to red to pink, and it feels soft or spongy when you press on it. Light pressure may cause thick, yellow fluid to drain from it. This bump is actually the opening of a drainage channel that the infection has created from the tooth root through the bone and gum tissue to reach the surface.
These bumps can be as small as a few millimeters or swell to the size of a marble. They tend to appear right next to the affected tooth, usually near the root tip. You might notice the bump comes and goes: it swells with pressure, drains on its own (leaving a foul taste in your mouth), then refills. This cycle doesn’t mean the infection is healing. It means the abscess has found a temporary outlet but the underlying infection remains.
Gum Abscess vs. Tooth Root Abscess
Not all dental abscesses look the same because they form in different locations. A periapical abscess starts deep inside the tooth, at the tip of the root, and the swelling eventually pushes outward through the gum near that root. You may not see anything on the surface at first, only feel deep, throbbing pain. As it progresses, the gum near the root swells and reddens.
A periodontal abscess forms in the gum tissue itself, typically in an existing gum pocket alongside a tooth. It looks like a darker, swollen bump directly on the gum line. It tends to be more immediately visible because the infection sits closer to the surface from the start. Both types can produce pus, but a periodontal abscess is often easier to spot early because the swelling is right at the gum surface rather than buried under bone.
What the Tooth Itself Looks Like
The affected tooth may also change in appearance. A tooth with a dying or dead nerve can gradually darken, shifting to a gray, brownish, or yellowish tone compared to the teeth around it. This discoloration happens because the blood supply inside the tooth has been compromised by infection, and breakdown products from the dying tissue stain the tooth from within. The darkening can also extend along the gum line near the tooth. You might also notice a visible cavity, crack, or broken filling on the tooth that served as the entry point for bacteria.
Pus Color and Drainage
The pus from a dental abscess is typically thick and yellow. It can also appear tan, gray, or brownish, especially if it has been accumulating for a while or contains blood. When an abscess drains, either on its own or when you inadvertently press on it, you’ll likely notice a sudden salty, bitter, or metallic taste and temporary relief of pressure. The fluid may have a strong, unpleasant smell. If the drainage appears greenish or is mixed with significant blood, the infection may be more aggressive.
How It Differs From a Canker Sore
People sometimes confuse an abscess with a canker sore because both can appear as spots on the gum tissue, but they look quite different up close. A canker sore is a small, flat, shallow ulcer with a white or yellow center and a clean red border. It sits flush with or slightly below the surrounding tissue. An abscess, by contrast, is a raised, swollen bump filled with pus. It projects outward from the gum and has no defined border or crater shape. Canker sores also appear on soft tissue like the inner cheeks, lips, or tongue, while abscesses almost always form on the gum right next to a tooth.
When Swelling Spreads Beyond the Gum
An abscess that isn’t treated can spread beyond the immediate area around the tooth. The infection can move into the soft tissues of the jaw, floor of the mouth, or cheeks, causing visible swelling on the outside of the face. This is called cellulitis, and it looks dramatically different from a localized gum bump. One side of the face may become noticeably puffy or asymmetrical. The skin over the swelling may feel warm, tight, and tender to the touch.
Facial or neck swelling from a dental infection is a serious situation. If swelling spreads to the neck or under the jaw, or if it causes difficulty breathing or swallowing, the infection has moved into deeper tissue planes that can compromise your airway. This requires emergency medical attention, not a scheduled dental visit.
What a Dentist Sees on X-Ray
Some abscesses aren’t visible from the outside at all, especially in early stages. On a dental X-ray, an abscess appears as a dark shadow or halo around the tip of the tooth’s root. Healthy bone shows up as a solid white or light gray area on X-rays. When an abscess destroys bone tissue around a root tip, that area loses density and appears as a dark circle. This is often how abscesses are caught before they produce any visible swelling, particularly during routine dental exams when symptoms are still mild.