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Canker sore causes and remedies

Published: July 19, 2023 |5 minute read

Written by: Lauren Arcuri

Woman gargling a solution to help with canker sore pain.

What to do when those fiery little bumps crop up inside your mouth — so you can feel better fast.

It starts with a suspicious tingle. Within hours, a swelling, achy red spot appears inside your cheek, which then erupts into a burning canker sore. Mealtime becomes a minefield, with every other bite creating the opportunity for a painful chomp. Experts estimate that about 10 percent of people get canker sores on a regular basis.

In this article:

Learn what steps you can take to help put out the fire.

What are canker sores?

Also known as aphthous ulcers, canker sores look like small, white-reddish blisters inside your mouth. They can appear on the gums, tongue, roof of the mouth or soft tissue on the inside of the lip. Canker sore symptoms depend on the stage of the sore and may include a tingling sensation when the sore is taking shape and pain and sensitivity once the sore has appeared. Experts don’t fully understand how canker sores form, and your likelihood of getting one (or many) is linked to a number of factors.

What causes a canker sore?

Canker sores can be brought on by certain triggers, including injury (like accidentally biting down on the inside of your cheek) or irritation (due to food sensitivity). Some people experience them with hormonal swings from stress or menstrual cycles, says Robert Stone, MD, a physician at Central Ohio Primary Care in Columbus, Ohio. Genetics may play a role, so if your parents get them, you might, too. Studies suggest that vitamin and mineral deficiencies (B vitamins and iron in particular) can make them more likely.

Canker sores versus cold sores

One telltale sign to tell them apart: A canker sore only forms inside your mouth. Typically, a canker sore looks like a white or yellow center surrounded by a bright red swelling.

A cold sore (also known as a fever blister) usually forms on your lips and is always outside your mouth. Cold sores are caused by a common viral infection: the herpes virus, usually the subtype HSV-1. If you have a cold sore, over-the-counter products like Abreva Docosanol 10% Cream tube may help shorten the duration of symptoms and potentially provide some relief.

How long does a canker sore last?

A small canker sore will typically be painful for only three to five days, but it can take much longer for them to go away completely. One to two weeks is typical, says Dr. Stone, though they can last as long as four weeks for larger canker sores.

Are canker sores contagious?

Unlike cold sores, which are caused by the highly contagious herpes simplex virus, canker sores are not contagious — you can’t catch them or spread them.

How to find symptom relief for a canker sore

Home remedies for canker sores

You can try a salt-and-baking-soda rinse, says Dr. Stone. Mix some table or sea salt and baking soda with warm water. Stir and swish in your mouth before spitting it out.

Avoid foods that might irritate your inflamed mouth more, including very acidic or salty foods, alcohol, fizzy drinks, or hard foods like crisp breads. Soups and soft foods might be more comfortable. Keep food temperatures cool or warm.

Relief support products for canker sores

If the canker sore isn’t too bothersome, a pain reliever may not be needed. But if you’re in pain, some over-the-counter treatments may help reduce the discomfort. Gels or liquids that contain benzocaine, a topical numbing agent, may help reduce pain. Products that cover the sore to prevent you from biting on it can help as well.

Your doctor might prescribe a mouthwash with a germ-killing ingredient like chlorhexidine. But be sure to avoid alcohol-based rinses that might aggravate pain.

When should you see your doctor for a canker sore?

If at-home treatments don’t help or if you’re in pain that gets in the way of daily life, you should see a health care provider. Your doctor may prescribe a steroid (in pill or cream form) or cauterize the inflamed tissue with silver nitrate or lasers.

Also seek medical care if your canker sore is unusually large (one centimeter or larger in diameter), if more than a few appear at one time or if your canker sore doesn’t resolve over a couple of weeks.

*This content is for informational purposes only and is not medical advice. Consult with your health care provider before taking any vitamins or supplements and prior to beginning or changing any health care practices.