Canker Sore

Canker sore

Key points

  1. A canker sore is an open and painful mouth ulcer or sore.
  2. Canker sores commonly appear when people are between 10 and 20 years of age.
  3. Canker sores usually heal without treatment. However, there are things you can do to relieve symptoms.

A canker sore, or aphthous ulcer, is an open and painful mouth ulcer or sore. It’s also the most common type of mouth ulcer. Some people notice them inside their lips or cheeks. They’re usually white or yellow and surrounded by red, inflamed soft tissue.

A canker sore can be simple or complex. A simple canker sore reemerges about three to four times every year and it commonly appears when people are between 10 and 20 years of age. A complex canker sore isn’t as common and develops in people who’ve had one before.

Neither type of canker sore is contagious. Both usually heal within one to three weeks without treatment, although the pain normally goes away in seven to 10 days. Serious canker sores may take up to six weeks to heal.

Contact your doctor or dentist if you develop:

  • large sores
  • an outbreak of sores
  • excruciating pain
  • a high fever
  • diarrhea
  • a rash
  • a headache

Seek medical care if you’re unable to eat or drink or your canker sore hasn’t healed within three weeks.



Pictures of a canker sore


What are the symptoms of a canker sore?

Canker sore symptoms include:

  • a small white or yellow oval-shaped ulcer in your mouth
  • a painful red area in your mouth
  • a tingling sensation in your mouth

In some cases, other symptoms may also be present, including:

  • swollen lymph nodes
  • a fever
  • not feeling well

See your doctor if a canker sore doesn’t heal on its own within three weeks. This could be a symptom of mouth cancer.

Cold sores

Cold sores are similar to canker sores. However, unlike canker sores, cold sores can appear outside of your mouth. Cold sores also appear first as blisters, not inflamed sores, and become sores after the blisters pop. Cold sores are caused by the herpes simplex virus (HSV). This virus is carried within your body and can be triggered by stress, exhaustion, and even sunburn. You can also get cold sores on your lips, nose, and your eyes.


Causes and risk factors

What are the causes and risk factors?

Your risk for developing canker sores increases if you have a family history of canker sores. Canker sores have various causes, and the most common ones include:

  • viral infection
  • stress
  • hormonal fluctuations
  • food allergy
  • menstrual cycle
  • vitamin or mineral deficiency
  • immune system problem
  • mouth injury

A deficiency in certain vitamins, such as B-3 (niacin), B-9 (folic acid), or B-12 (cobalamin), can make you more prone to getting canker sores. Zinc, iron, or calcium deficiencies can also trigger or worsen canker sores.

In some cases, the cause of a canker sore can’t be determined.

Read more: The symptoms of vitamin B deficiency »


How is a canker sore diagnosed?

Your doctor can usually diagnose a canker sore by examining it. They may order blood tests or take a biopsy of the area if there’s a severe breakout or if they think you might have:

  • a virus
  • a vitamin or mineral deficiency
  • a hormonal disorder
  • a problem with your immune system
  • a severe breakout

A cancerous lesion may appear as a canker sore, but it won’t heal without treatment. Some symptoms of oral cancer are similar to those of canker sores, like painful ulcers and swelling in your neck. But oral cancer is often indicated by unique symptoms, including:

  • bleeding from the mouth or gums
  • loose teeth
  • trouble swallowing
  • earaches

If you experience these symptoms along with canker sore symptoms, see your doctor right away to rule out oral cancer as a cause.



How is a canker sore treated?

Canker sores usually heal without treatment. However, there are many helpful lifestyle changes you can make. Brush and floss your teeth regularly to prevent a bacterial infection. Avoid spicy foods to speed up the healing process. Drinking milk or eating yogurt or ice cream can also help reduce the pain.

Pain can sometimes be severe. You can lessen the discomfort by gargling with mouthwash or salt water. It will feel uncomfortable at first, but it will help reduce pain.

Some ingredients in over-the-counter topical products can help relieve and heal sores, including:

  • benzocaine, found in Orabase, Zilactin-B, or Kank-A
  • hydrogen peroxide, found in peroxyl and Orajel antiseptic rinses
  • fluocinonide, found in Vanos

Your doctor or dentist may prescribe:

  • an antimicrobial mouth rinse, such as Listerine or mouth rinses with chlorhexidine gluconate
  • an antibiotic, such as mouthwashes or pills with doxycycline
  • a corticosteroid ointment, such as hydrocortisone hemisuccinate or beclomethasone
  • a prescription mouthwash, especially one that contains dexamethasone or lidocaine for inflammation and pain

Alternative and home treatments

What are some home remedies for canker sores?

Applying ice or tiny amounts of milk of magnesia to your sores can help relieve pain and promote healing. Rinsing your mouth with warm water and a teaspoon of baking soda (per 1/2 cup of water) can also help with pain and healing. Honey has been shown to be effective in treating canker sores.



What are the complications of canker sores?

If your canker sore is left untreated for a few weeks or more, you may experience other, more serious complications, such as:

  • discomfort or pain while talking, brushing your teeth, or eating
  • fatigue
  • sores spreading outside of your mouth
  • fever
  • cellulitis

See your doctor if your canker sore is causing you unbearable pain or interfering with your life, and home treatments aren’t working. And contact your doctor even if these complications happen within a week or two of the sore developing. Bacterial infections can spread and create more serious issues, so it’s important to stop a possible bacterial cause of a canker sore quickly.

Learn more: Cellulitis »


Tips to prevent canker sores

You can prevent the recurrence of canker sores by avoiding foods that may have previously triggered the outbreak. These often include spicy, salty, or acidic foods. Also, avoid foods that cause allergy symptoms, such as an itchy mouth, a swollen tongue, or hives.

If a canker sores pops up due to stress, use stress reduction methods and calming techniques, such as deep breathing and meditation.

Practice good oral health and use a soft toothbrush to avoid irritating your gums and soft tissue. Talk to your doctor to determine if you have any specific vitamin or mineral deficiencies. They can help design a suitable diet plan and prescribe individual supplements if you need them.

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