A swollen gum around one tooth in the back of your mouth usually points to a localized infection or irritation, not a widespread gum problem. The most common culprits are a partially erupted wisdom tooth, a trapped piece of food or debris, or an abscess forming near the tooth’s root or gum line. Most cases resolve with treatment within days to a few weeks, but certain warning signs mean you shouldn’t wait.
Pericoronitis: The Most Likely Cause
If the swollen tooth is a wisdom tooth, or the molar right in front of one, the leading suspect is pericoronitis. This happens when a wisdom tooth only partially breaks through the gum, leaving a flap of tissue (called the operculum) draped over part of the tooth. That flap creates a pocket where food particles, bacteria, and debris collect easily. Because it’s nearly impossible to clean under this flap with normal brushing, the area becomes inflamed and infected quickly.
Pericoronitis typically shows up in your late teens or early twenties, when wisdom teeth are trying to come in, but it can happen at any age if a wisdom tooth remains partially erupted. You’ll notice the gum tissue around the tooth looks red and puffy, feels tender to the touch, and may throb or ache when you chew. In more advanced cases, the flap itself can swell enough that you accidentally bite down on it, making things worse. A bad taste in your mouth or minor bleeding when brushing the area are also common.
Trapped Food and Debris
Sometimes the explanation is surprisingly simple. A popcorn hull, seed, or small piece of food wedged beneath the gum line can trigger intense localized swelling within a day or two. Back molars are especially vulnerable because they have deep grooves and tighter spaces that trap debris more easily. If you recently ate something fibrous or crunchy and the swelling appeared shortly after, this is worth considering. Gentle flossing and warm salt water rinses can often dislodge the particle, and the swelling starts to calm once the irritant is gone.
Gum Abscess vs. Tooth Abscess
When the swelling is more intense, painful, or accompanied by a visible bump on the gum, an abscess may be forming. There are two types, and they feel different.
A gum-based (periodontal) abscess starts in the tissue surrounding the tooth rather than inside it. The pain tends to worsen when you bite down, and the tooth may feel slightly loose or like it’s sitting higher than usual. You might notice a raised, oval-shaped bump on the gum alongside the root. The tooth itself is still alive and healthy inside; the problem is the pocket of infection in the surrounding tissue.
A tooth-based (periapical) abscess originates from damage inside the tooth, usually from a deep cavity, crack, or old filling that allowed bacteria to reach the nerve. The pain is often more constant and can radiate into your jaw or ear. You may notice increased sensitivity to hot or cold, or the tooth may have stopped responding to temperature entirely, which signals the nerve inside has died. A small pimple-like bump on the gum near the root tip can appear as the infection tries to drain.
Both types require professional treatment. Neither will resolve on its own, and delaying care gives the infection time to spread into the surrounding bone.
What You Can Do at Home
Home care won’t fix the underlying problem, but it can manage pain and reduce swelling while you wait for a dental appointment. A warm salt water rinse is the simplest option: dissolve half a teaspoon of salt in a cup of warm water, swish gently for 30 seconds, and spit. Repeat two to three times a day. The salt draws fluid out of swollen tissue and creates an environment that’s harder for bacteria to thrive in.
Over-the-counter anti-inflammatory pain relievers can help with both the swelling and discomfort. Avoid placing aspirin directly on the gum, as this burns the tissue. If you suspect food is trapped, try gently working dental floss or an interdental brush around the tooth, but stop if it causes significant pain or bleeding. An alcohol-free antibacterial mouthwash containing chlorhexidine or hydrogen peroxide can also help keep bacterial levels down.
What Professional Treatment Looks Like
Your dentist will first figure out what’s causing the swelling, typically with a visual exam and an X-ray of the area. Treatment depends on the diagnosis.
For pericoronitis, mild cases are treated with a thorough cleaning of the area and a course of antibiotics if infection is present. If the flap of gum tissue keeps causing problems, a minor procedure to remove it may be recommended. In many cases, the long-term fix is extracting the wisdom tooth so the problem doesn’t recur.
For gum disease localized to one tooth, scaling and root planing is the standard approach. This is a deep cleaning done under local anesthesia where your dentist or hygienist removes plaque and tartar buildup beneath the gum line and smooths the root surface so bacteria have a harder time reattaching. Antibiotic medication can be placed directly into the pocket between the gum and tooth to fight remaining infection.
For an abscess, the priority is draining the infection. If the tooth itself is damaged, a root canal or extraction may follow. If the infection is in the surrounding gum tissue, cleaning the pocket thoroughly and sometimes reshaping the bone underneath allows the area to heal. Your dentist repositions the gum tissue and sutures it into place.
How Long Recovery Takes
Swelling from simple causes like trapped food or mild gingivitis often resolves within a few days once the irritant is removed or a cleaning is done. More established gum infections treated with scaling and root planing typically improve noticeably within a week, with full tissue healing taking a few weeks. Abscess drainage usually brings significant pain relief within 24 to 48 hours, though the underlying repair (root canal, extraction, or gum surgery) has its own recovery timeline.
If your swelling hasn’t improved after two weeks, or if it’s getting worse rather than better, that’s a clear signal to get professional evaluation rather than continuing to manage it at home.
Signs That Need Urgent Attention
Most localized gum swelling is uncomfortable but not dangerous. A few specific symptoms change that picture. Facial swelling that spreads beyond the gum into your cheek or jaw, fever, difficulty swallowing, or trouble opening your mouth all suggest the infection is spreading beyond the tooth. Untreated dental abscesses can lead to sepsis or bone damage. A bad taste combined with swelling that’s rapidly worsening also warrants same-day care rather than a scheduled appointment. These situations are genuine dental emergencies, not something to ride out over the weekend.