What can you do if you have a canker sore?

Photo of a teenager holding an apple (PantherMedia / Lars Hallstrom)

Canker sores (mouth ulcers) usually heal on their own within a few days. Gels, creams or mouthwashes can help to relieve the pain. In severe cases, steroid tablets may be considered.

It’s not known why canker sores develop. That’s why the treatment focuses on the symptoms instead of the cause. It aims to relieve the acute symptoms and support the healing process.

Is treatment always necessary?

If the symptoms are bearable, then treatment isn't needed. This is most likely the case for the more common minor canker sores: 85 out of 100 people who have canker sores have this type, which is the mildest. Minor canker sores are only a few millimeters wide, are painful for three to five days, and go away completely after about two weeks.

What foods should you avoid or eat?

During the phase of acute inflammation, it's helpful to avoid certain foods that can irritate the inflamed mucous membranes even more – such as crispy or hard foods like bread rolls or crispbread (such as Ryvita). Very acidic, spicy or salty foods can also be unpleasant, as can fizzy drinks or alcohol. But you should still make sure that you don’t eat too much of the same thing, or too little overall. Eating soups and soft foods can help to protect the mucous membranes. It's also a good idea to let any food that you cook cool off enough or to eat cold meals.

If you think that certain foods or oral hygiene products are encouraging the development of canker sores, then try avoiding them. But there's a lack of good research on whether a certain diet can delay the formation of new canker sores.

Oral hygiene: What you need to know

Even though moving your mouth can make the pain worse, you should brush your teeth just as well as you usually do when you don’t have a canker sore. A soft brush can help to prevent injuries to your gums that could increase the risk of new canker sores developing. There are various ways to clean the spaces between your teeth – for instance, with an interdental brush or dental floss. You can ask your dentist for advice to help you find the right option for you.

It’s also important to check the ingredients used in the oral hygiene products: Mouthwashes that contain alcohol may make the pain worse, for instance. Some people also react sensitively to toothpaste that has sodium lauryl sulfate in it.

What can help relieve the symptoms?

Various kinds of medications can be used to treat canker sores. They can be applied to the sores in the form of a gel, cream, paste or spray. Some are also available as a mouthwash or lozenges:

  • Local anesthetics: Local anesthetics like lidocaine or benzocaine can dull the pain. They are typically applied to the sores as a gel or cream.
  • Anti-inflammatory drugs: Some medicines contain the painkiller diclofenac, which is an NSAID. Diclofenac can relieve pain and reduce inflammation.
  • Antiseptic drugs: Mouthwashes with germ-killing ingredients like chlorhexidine or triclosan are used to stop germs from growing in the wound and delaying the healing process or making the inflammation worse.
  • Plant-based remedies (astringents): Tinctures made from myrrh or rhubarb root help some people. These plant-based remedies cause the blood vessels in the mucous membranes to become narrower, which is believed to relieve the pain.

What can you do if these things don't help?

If treating canker sores with local anesthetics, painkillers or antiseptic medications doesn't help, you can apply steroid creams. If those aren't effective or if the sores are very severe, it's a good idea to see a doctor or dentist. They can cauterize (destroy) the inflamed tissue – for instance, using a silver nitrate solution or laser treatment.

When are tablets needed?

About 15 out of 100 people who keep on getting canker sores have large inflammations or an especially large number of them. Some of them then have such severe pain that it becomes difficult to eat, drink or sleep – especially if the canker sores heal only gradually or constantly come back.

In these rare, severe cases, it may be a good idea to take tablets in addition to using a local treatment – for instance, steroid tablets. They have an effect both on the membranes lining the mouth and the rest of the body (systemic treatment). But side effects may be more common then.