Swollen Gum With Pus (Dental Abscess): What to Do Now

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A swollen gum with pus is usually a dental abscess: an infection that builds up at the tip of the root of a tooth whose nerve is damaged, or in a gum pocket. What to do now: don't squeeze or pop the bump, don't put heat on your face, rinse gently with warm salt water, take only the pain reliever you normally use, and see a dentist within 24 hours. If you have facial swelling with fever, or trouble swallowing, breathing or opening your mouth, go to a hospital emergency room right away.

In practice, patients often come in after days with a "bump" on the gum that fills up, bursts and comes back, or with a toothache that suddenly got better once the swelling appeared. That relief is misleading: when the pus finds a way out, the pressure drops and the pain eases, but the infection is still active. Antibiotics alone don't solve it either, because the cause is in the tooth or the gum.

Below, Dr. Cléo Salustiano (CRO-SP 170844), a dentist in Mooca, explains how to recognize an abscess, what to do in the first few hours, when it is a medical emergency, and how the dentist treats the cause — usually with root canal treatment, gum treatment or, when the tooth can't be saved, an extraction.

This article comes from Dr. Cléo Salustiano's dental office in Mooca, São Paulo (care in English, Portuguese and Spanish). See the root canal treatment page to learn how the treatment is done here and book your assessment.

Step by step

1. Don't squeeze or pop the pus bump. Pressing it or poking it with a needle can spread the infection to nearby tissue and injure the gum. If the bump bursts on its own, rinse your mouth with warm water.
2. Don't put heat on the outside of your face. A hot water bottle on your face can encourage the infection to spread outward. To ease swelling, use a cold compress on the outside instead, for short periods, with a cloth between the ice and your skin.
3. Rinse gently with warm salt water. Half a teaspoon of salt in a glass of warm water, swished gently a few times a day, helps clean the area. It doesn't replace treatment, but it brings relief and keeps the area cleaner.
4. Take only the pain reliever you normally use. Follow the label dose or your doctor's advice. Don't put a pill on the tooth or gum, because it burns the tissue. Don't start antibiotics on your own or use leftovers from a previous treatment.
5. See a dentist within 24 hours — or go to the ER if there are warning signs. Swelling that spreads across the face or neck, fever, trouble swallowing, breathing or opening your mouth, and feeling generally unwell are reasons to go to a hospital emergency room now. Without these signs, book a dental visit for the same day or the next.

What is a dental abscess and why does it happen?

A dental abscess is a pocket of pus caused by a bacterial infection. It shows up as a swollen gum, sometimes with a yellowish or white bump, pain, a bad taste in the mouth and tenderness when chewing. The two most common types are the abscess at the tip of the root, linked to the tooth's nerve, and the gum abscess, linked to a periodontal pocket. Knowing which one you have determines the treatment.

An abscess at the root tip, called a periapical abscess, usually starts when a deep cavity, a crack or an old leaking filling lets bacteria reach the nerve. The nerve becomes inflamed and dies, and the infection travels down the canal to the tip of the root, forming pus in the bone. There is often a history of strong pain that later "went away," or of a tooth that turned darker.

A periodontal abscess starts in the gum, around a tooth with gum disease: the pocket between the tooth and gum collects plaque and food debris and becomes infected. It can appear even on a tooth with no cavity and a healthy nerve. People with untreated gingivitis or periodontitis, poorly controlled diabetes, or food stuck in the gum are at higher risk.

The "bump" that fills and bursts on the gum is called a fistula (or sinus tract): it is the path the pus found to drain. It relieves pressure and pain, which leads many people to put off treatment. But the infection continues, can destroy the bone around the root and, in some cases, spread. That's why a fistula needs to be checked too, even without pain.

Signs that the infection is spreading call for urgent medical care: swelling that grows and extends to the face, under the chin or the neck; a swollen eye; fever; trouble swallowing, breathing or opening your mouth; and feeling generally unwell. These situations are rare, but they can't wait for a dental appointment.

How does a dentist treat a dental abscess?

The dentist treats a dental abscess by removing the source of the infection and letting the pus drain. When the abscess comes from the nerve, this usually means opening the tooth and starting root canal treatment. When it comes from the gum, it means deep cleaning of the pocket and drainage. When the tooth is badly broken down or has a crack that can't be repaired, extraction may be recommended.

Antibiotics are used in specific situations, such as spreading swelling, fever or feeling generally unwell, and always prescribed by a professional. They help control the infection but can't solve it alone, because they don't reach the inside of a tooth with a dead nerve or clean a gum pocket. That's why an abscess often comes back when only medication is taken.

Treatment continues after the emergency visit. In root canal treatment, the inside of the tooth is cleaned, disinfected and sealed over the following visits, and the tooth then needs a filling or crown so it doesn't fracture. With a periodontal abscess, the gums are treated as a whole to prevent new pockets. In both cases, follow-up visits monitor how the bone heals.

In the days after treatment, pain and swelling usually ease gradually. Keep brushing the area carefully, avoid chewing on the tooth until the final restoration, and follow the medication instructions. If the pain gets worse, the swelling grows or you develop a fever, let your dentist know.

In Mooca, Dr. Cléo Salustiano sees dental emergencies every day from 8 a.m. to 10 p.m., by appointment via WhatsApp. No one can guarantee that a tooth with an abscess will be saved — that depends on how much the infection has affected the tooth and bone — but seeking care early improves the chance of simpler treatment.

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