Pericoronitis: Swollen Gum Around a Wisdom Tooth

Pericoronitis is an infection of the gum flap sitting over a partly erupted wisdom tooth. It causes a swollen, throbbing gum at the back of the mouth, often with a foul taste, and it tends to come back until the underlying situation is dealt with.

What Pericoronitis Actually Is

When a wisdom tooth only comes partway through, a hood of gum stays over part of it. That hood is called an operculum, and the space beneath it is the problem.

The gap between gum and tooth is deep, narrow and impossible to clean with a toothbrush. Food debris and bacteria collect there and stay there. Eventually the tissue becomes infected, and that infection is pericoronitis.

The key thing to understand is that this is not a problem with the tooth itself. The tooth may be perfectly healthy. It is the pocket of unreachable gum around it that causes trouble, which is why cleaning your teeth better rarely prevents a recurrence.

Why it keeps happening

Once you have had pericoronitis, you are considerably more likely to have it again, because nothing about the anatomy has changed. The operculum is still there and the pocket underneath is still uncleanable.

Each episode also tends to make the tissue slightly more inflamed and scarred, so flare-ups can become more frequent over time. Repeated episodes are one of the clearest reasons dentists recommend removing a wisdom tooth.

Symptoms, Mild Through to Serious

Early and mild

• Tender, puffy gum behind the last tooth
• Sore when you bite, because the upper tooth presses the swollen flap
• Unpleasant taste or a smell you notice when you press the area
• Mild ache that comes and goes

Established infection

• Throbbing pain, often radiating to the ear or jaw on that side
• Visibly swollen, red gum, sometimes with a whitish edge
• Pus when the area is pressed, and a persistent bad taste
• Swollen lymph nodes under the jaw on that side
• Difficulty opening the jaw fully, called trismus

Needs urgent care

• Swelling spreading across the cheek or down towards the neck
• Fever or feeling generally unwell
• Difficulty swallowing or breathing
• A jaw that will barely open

Those last four mean the infection is no longer contained. Lower wisdom teeth sit close to the spaces around the airway, and spreading infection there is treated as a medical emergency. Go to A&E rather than waiting for a dental appointment.

How Long It Lasts

With treatment, mild cases usually start improving within three to five days and settle within a week or two.

Moderate cases involving real swelling take seven to fourteen days to resolve fully.

Without treatment, it may quieten down on its own after a week or two, and this is where people get caught out. The symptoms fading is not the same as the problem being solved. The operculum remains, and most people get another episode within months.

What a Dentist Does About It

Treatment happens in two stages, and they answer different questions: settle this episode, then prevent the next one.

Settling the current infection

Irrigation and debridement. The pocket under the gum flap is flushed out and cleaned, usually with an antiseptic solution and a fine tip that reaches where a toothbrush cannot. This alone often brings noticeable relief within a day, because it removes what the infection is feeding on.

Adjusting the bite, occasionally. If the opposing upper tooth is repeatedly traumatising the swollen flap, smoothing that cusp slightly takes the pressure off.

Antibiotics, where the infection has spread beyond the gum, where there is facial swelling, fever, or a jaw that will not open. They are not automatic. Pericoronitis confined to the gum flap usually responds better to physical cleaning than to tablets, and our guide to antibiotics for tooth infections explains when they genuinely help.

Preventing recurrence

This is the decision that matters, and there are two routes.

Removing the wisdom tooth. The definitive answer. No tooth, no operculum, no pocket. Usually recommended after repeated episodes, or where the tooth is impacted and never going to erupt properly.

Removing just the gum flap, an operculectomy. The hood of tissue is trimmed away so the pocket disappears while the tooth stays. This suits a specific situation: a tooth that is genuinely on its way to erupting fully and just needs the gum out of the way. It is less useful where the tooth is impacted, because the flap tends to reform.

Which applies to you depends on an X-ray showing whether the tooth has anywhere to go. Our page on impacted wisdom teeth covers what the different patterns mean, and wisdom tooth pain sets out the broader picture if you are not sure this is what you have.

What You Can Do at Home

Home care helps a mild episode and buys time before an appointment. It does not cure the underlying problem.

Warm salt water rinses, frequently, and vigorously enough to actually reach the area. This is the single most useful thing on the list, because it physically flushes debris out of the pocket. Every few hours, and after every meal.

Clean the area even though it hurts. Most people stop brushing where it is sore. A small-headed or single-tuft brush angled behind the last tooth reaches further than a standard brush.

A syringe or interdental brush to irrigate under the flap, if your dentist has shown you how. Do not improvise this with anything sharp.

Cold on the outside of the cheek for swelling, twenty minutes at a time.

Soft food, chew on the other side, and prop your head up at night.

Over-the-counter pain relief as directed on the packet. A pharmacist will confirm which suits you.

What to avoid: heat on a swollen face, poking the flap with anything, and assuming it will be fine because it settled last time.

Frequently Asked Questions

Will pericoronitis go away on its own?

The symptoms often fade after a week or two, but the cause does not go anywhere. The gum flap and the pocket under it remain, so recurrence is likely. Treating it properly is what stops the cycle.

Is pericoronitis serious?

Usually it is a contained gum infection and straightforward to treat. It becomes serious if it spreads, which shows as facial swelling, fever, difficulty swallowing or a jaw that will barely open. Those need urgent care.

Do I need antibiotics for pericoronitis?

Not always. Confined to the gum flap, physical cleaning of the pocket usually works better. Antibiotics are for cases with spreading swelling, fever or restricted jaw movement.

Can I treat pericoronitis at home?

You can settle a mild episode with frequent salt water rinsing and careful cleaning. You cannot remove the pocket that caused it, so home care is management rather than treatment.

Does pericoronitis mean the wisdom tooth has to come out?

Not necessarily after one episode, particularly if the tooth is erupting properly and just needs the gum trimmed. After repeated episodes, or where the tooth is impacted, removal is usually the sensible answer.

Why can I not open my jaw properly?

Inflammation reaching the muscles that close the jaw causes them to spasm, which is called trismus. It is common with established pericoronitis and it counts as a reason to be seen promptly.

How long does pericoronitis take to heal after treatment?

Mild cases improve within three to five days and settle inside a week or two. Cases with significant swelling take up to a fortnight.

Can pericoronitis affect the tooth in front?

Yes, and this is one of the better arguments for dealing with it. The uncleanable pocket sits against the back surface of your second molar, which is a healthy and useful tooth. Decay there is common and awkward to restore.

Same-Day Appointments in Elephant & Castle

Pericoronitis responds quickly to having the pocket properly cleaned out, and that is not something you can do yourself. If the gum at the back of your mouth is swollen and tasting bad, it is worth getting in rather than riding it out.

Call 020 7928 4474 or book online. We hold emergency slots each day, and our emergency dentist page lists what we can deal with same-day. If a tooth does need removing, extractions start from £195.

This page is general information, not a diagnosis. Spreading facial swelling, fever or difficulty swallowing needs urgent medical care rather than a dental appointment. Last reviewed August 2026.