Pericoronitis: The Gum Infection Around a Wisdom Tooth

Editorially reviewed by the Dental.me Editorial Team · Updated July 2026

If the very back of your lower jaw is sore, swollen, and tastes bad, and there is a wisdom tooth only halfway through the gum, you may be dealing with pericoronitis. It is one of the most common problems dentists see with wisdom teeth, and it has a habit of flaring up, settling down, and then coming back again. The good news is that a mild episode often calms with careful cleaning and salt water. The important news is that a spreading version can become a genuine emergency, so it helps to know the difference. This guide walks through what pericoronitis is, why it happens, how to manage a mild case at home, when to see a dentist, and the warning signs that mean you should not wait.

What pericoronitis actually is

Pericoronitis is inflammation and infection of the gum tissue around a tooth that has only partly come through. The word itself simply means “around the crown.” In the vast majority of cases the tooth involved is a lower wisdom tooth (third molar) that has erupted part of the way but not fully.

When a tooth is only partially erupted, a small flap of gum tissue often sits over part of the biting surface. Dentists call this flap the operculum. That flap creates a pocket between the gum and the tooth. It is a warm, moist, sheltered space that traps food debris and bacteria, and it is almost impossible to clean out with a normal toothbrush. Over time the trapped bacteria irritate the tissue, the flap swells, and an infection sets in. Sometimes the flap is even nicked by the opposing upper tooth when you bite down, which makes the swelling and soreness worse.

Why wisdom teeth are the usual culprit

Wisdom teeth are the last teeth to arrive, usually in the late teens or twenties, and there is frequently not enough room left in the jaw for them to come through cleanly. A tooth that is wedged or angled and cannot fully erupt is described as an impacted wisdom tooth, and a partially erupted, impacted lower wisdom tooth is the classic setting for pericoronitis. The tooth is through just enough to open a doorway for bacteria, but not enough to be cleanable, which is the worst of both worlds.

This is also why pericoronitis matters beyond the immediate discomfort. Repeated infections around the same tooth are one of the most common reasons dentists and oral surgeons recommend taking the tooth out. If you are weighing that decision, it is worth reading about whether you need your wisdom teeth removed, because recurrent pericoronitis is a strong point in favor of extraction.

Symptoms to look for

Pericoronitis usually announces itself at the very back of the jaw, and the signs range from mildly annoying to clearly serious.

• Pain, soreness, or a dull ache at the back of the jaw, often on one side
• A red, swollen, tender flap of gum over or around the erupting tooth
• A bad taste in the mouth or visible pus oozing from under the flap
• Persistent bad breath
• Swelling of the gum and cheek near the tooth
• Difficulty or pain when opening the mouth, biting, or chewing
• Tender, swollen glands (lymph nodes) under the jaw or in the neck
• In more serious cases, fever and noticeable facial swelling

Acute versus chronic pericoronitis

Dentists often describe the problem as either acute or chronic. Chronic pericoronitis is the low-grade version: a mild recurring ache, a bad taste now and then, and mild tenderness that you might live with for months. Acute pericoronitis is a flare-up, with more intense pain, obvious swelling, pus, trouble opening the mouth, and sometimes fever. The same tooth can swing between the two, quiet for a while and then flaring, which is exactly why the problem tends to keep returning until the underlying flap or tooth is dealt with.

Self-care for a mild flare-up

If the episode is mild, with no fever and no spreading swelling, there are sensible steps that can settle it and buy time until you can see a dentist. These measures reduce the bacterial load and calm the tissue, but they do not remove the flap, so relief is often temporary.

• Warm salt-water rinses. Rinsing several times a day, especially after meals, helps flush debris from under the flap and soothes the gum. A simple salt-water rinse for teeth and gums is one of the most useful things you can do for a mild case. An antiseptic (for example chlorhexidine) mouthrinse can help too if your dentist recommends it.
• Meticulous cleaning of the flap area. Gently clean around and, as much as you can, under the flap. A small or single-tuft brush and careful, gentle irrigation with water can dislodge trapped food that a normal brush misses.
• Over-the-counter pain relief. Standard painkillers taken as directed on the label can manage the discomfort and reduce inflammation.
• Soft foods and care when biting. Sticking to soft foods and avoiding chewing directly on the sore area reduces trauma to the swollen flap.

Keep in mind the honest limitation here. Home care can quiet a mild flare, but as long as the gum flap remains and the tooth stays partly erupted, the food trap is still there. Pericoronitis very commonly recurs, which is the signal that professional treatment is needed rather than another round of rinsing.

Professional treatment: what a dentist will do

A dentist or oral surgeon can do things you cannot do at home. The first step is usually to clean and irrigate thoroughly under the flap to remove the trapped debris and bacteria, which often brings quick relief. If the infection is spreading, there is fever, or the swelling is significant, they may prescribe antibiotics to bring it under control. Note that antibiotics treat the infection but do not fix the flap or the crowding, so the problem can return once the course ends.

For recurring cases, the definitive fix is usually to remove the offending wisdom tooth, especially when it is impacted or has no useful partner to bite against. Occasionally, when the tooth is otherwise healthy, well-positioned, and worth keeping, a dentist may instead remove just the gum flap in a small procedure called an operculectomy. Which route makes sense depends on the position of the tooth, how often the infections come back, and the shape of your bite. It is worth distinguishing pericoronitis from a gum boil or dental abscess, which is a different kind of infection and may need different treatment, so a proper diagnosis matters.

Red flags: when it becomes an emergency

Most pericoronitis is uncomfortable but not dangerous. Occasionally, though, the infection spreads from the gum into the deeper tissue spaces of the jaw, floor of the mouth, and neck. That is a medical emergency because it can threaten the airway. Get urgent care from a dentist or the emergency room if you notice any of the following:

• Swelling that is spreading across the face, under the jaw, or down into the neck
• Difficulty swallowing, difficulty breathing, or a changed voice
• High fever or feeling generally very unwell
• Swelling that is getting rapidly worse over hours
• Being unable to open the mouth more than a little

A rare but serious deep-space infection called Ludwig’s angina can develop from an untreated lower tooth infection, and it needs emergency hospital treatment. If you are unsure how serious your situation is, our guide to what counts as a dental emergency can help you decide whether to wait for a regular appointment or seek care now. When in doubt with spreading swelling, treat it as urgent.

Preventing the next flare-up

You cannot always prevent a first episode, but you can lower the odds of repeats. Clean partially-erupted teeth carefully, paying attention to the awkward gum margin where flaps form. Keep up with regular dental checkups so your dentist can monitor how your wisdom teeth are coming through and catch trouble early. And if extraction is recommended for a tooth that keeps causing infections, having it done in a timely way, rather than after several more flares, usually spares you a lot of discomfort.

The takeaway

Pericoronitis is a common infection of the gum flap over a partly-erupted tooth, almost always a lower wisdom tooth. Salt-water rinses, diligent cleaning, soft foods, and pain relief can calm a mild flare, but because the underlying flap stays put, it tends to come back. That recurrence is your cue to see a dentist, who can clean under the flap, prescribe antibiotics if the infection is spreading, and, for repeat offenders, remove the tooth. Above all, treat spreading facial or neck swelling, trouble swallowing or breathing, or a high fever as an emergency and get urgent care straight away.

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