As mouth ulcers heal, their whitish color will fade, and any surrounding redness will start to go away. You’ll also feel less pain and burning. This could happen over 1–4 weeks.

Mouth ulcers are sores that develop in your mouth. They can be due to conditions such as hand, foot, and mouth disease or oral cancer. But many mouth ulcers are aphthous ulcers, also known as canker sores.

Canker sores aren’t usually serious and typically heal on their own without treatment. Still, they can be painful or uncomfortable during the healing process.

They most commonly occur on the inside of your cheeks or lips but can also form on the tongue, gums, or back of the mouth. It’s possible to have more than one canker sore at a time.

Read on if you have a mouth ulcer and want to know how long it will last. This article reviews what to expect when it’s healing.

Mouth ulcers typically heal on their own. The healing process can take anywhere from 1–4 weeks, depending on type:

  • Minor (simple) canker sores: These are usually less than 1 centimeter (0.4 inches) in size. They typically heal within 2 weeks.
  • Major canker sores: These are about 1–3 centimeters (0.4–1.2 inches) in size and may have irregular borders. They can take up to 4 weeks to heal.
  • Herpetiform canker sores: A cluster of tiny canker sores can join to form one large raised bump. Healing time varies from 2–4 weeks.

Wounds and sores in the mouth typically go through four stages:

1. Hemostasis

If a mouth ulcer causes you to bleed, your body will first try to reduce blood loss. This is known as hemostasis. Canker sores don’t typically bleed unless irritated or infected, but some mouth ulcers may cause bleeding.

2. Inflammation

Inflammation is what gives mouth ulcers like canker sores their typical appearance.

You’ll start to notice the formation of a swollen bump that may be red in color. You may also feel pain, roughness, or a burning sensation. Within 1–3 days, a white spot will appear.

A completely formed canker sore looks like a white or yellow round bump with a raised, red, inflamed border. People with darker skin tones may have canker sores with less redness than those with lighter skin tones.

3. Proliferation

Proliferation involves the growth of new skin. This starts from the outside of the ulcer and works its way toward the center.

As it starts to heal, the surrounding area of redness will dissipate. The central white part will take on a grayish tinge. Sensations like pain and burning will subside.

4. Maturation

As new skin tissue continues to form, the bump will diminish, and the tissue will start to regain its regular appearance.

The foods you eat can irritate an existing mouth ulcer, prolonging the healing process. Try to avoid spicy, salty, and acidic foods. Hot or carbonated drinks may cause discomfort, so consider avoiding those.

Also, avoid using mouthwash that contains alcohol and toothpaste containing sodium.

To hasten healing and make you feel more comfortable, consider these at-home remedies:

  • Take over-the-counter (OTC) pain relievers, which can reduce discomfort.
  • Rinse your mouth with warm salt water several times a day. Make a saltwater rinse by adding 1/2 teaspoon of salt to 1 cup of warm water. Stir until the salt dissolves.
  • Mix equal parts warm water with 3% hydrogen peroxide and apply to the canker sore with a cotton swab up to four times daily.
  • Apply OTC numbing medication to the canker sore as directed.
  • Apply magnesium hydroxide (milk of magnesia) directly to the sore with a cotton swab.

If you have a mouth ulcer that’s deep and painful or doesn’t improve within 3 weeks, contact a healthcare professional. They may prescribe medications that support healing in mouthwash, lotion, or pill form.

Let them know if you get canker sores more than two or three times a year.

Canker sores accompanied by any sign of infection require examination. Contact a healthcare professional if you notice any of these symptoms:

  • fever
  • pus or oozing
  • sore throat
  • runny nose
  • swollen lymph nodes (may cause tenderness or swelling in the neck, armpits, or groin)
  • fatigue
  • diarrhea
  • headache
  • skin rash

How can I prevent mouth ulcers?

Canker sores are common and have many causes, including hormonal changes, food allergies, and genetics. It may not be possible to prevent all occurrences of mouth ulcers, especially if they’re common in your family.

But these changes may help you prevent some mouth ulcers:

  • Use a soft or medium-soft toothbrush instead of a hard one, which can cause bruising.
  • If you use an electric toothbrush, don’t brush too vigorously or overly long.
  • Avoid biting the inside of your cheek or tongue.
  • Try to reduce stress, which may trigger mouth ulcers in some people.
  • Vitamin deficiencies may play a role, so eating a balanced diet that contains iron, folic acid, and vitamin B12 may help.
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Many mouth ulcers usually aren’t serious. Mouth ulcers like canker sores usually go away on their own within 1–4 weeks.

Contact a healthcare professional about a mouth sore that doesn’t improve within that time frame. They can check for causes that may be more serious. Accompanying symptoms such as fever and swollen lymph nodes also may require medical attention.