Canker sore causes and relief support options

It may start with a suspicious tingle. Within hours, a swelling, achy red spot appears inside the 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.¹

In this article:

What are canker sores?

Also known as aphthous ulcers, canker sores look like small, white-reddish blisters inside the mouth. They can appear on the gums, tongue, roof of the mouth or soft tissue on the inside of the lip or cheek. 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 why canker sores form, and the likelihood of getting one (or many) is possibly linked to several factors.²

What causes a canker sore?

Canker sores can be brought on by certain triggers, including injury (like accidentally biting down on the inside of the 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.³ Genetics also may play a role, so if a person’s parents get them, they might, too.⁴ Studies suggest that vitamin and mineral deficiencies (B vitamins⁵ and iron⁶ in particular) can make them more likely to get canker sores as well.

Canker sores versus cold sores

One telltale sign to tell them apart: A canker sore only forms inside the mouth.⁷ Typically, a canker sore has a white or yellow center surrounded by a bright red swelling.⁸

A cold sore (also known as a fever blister) usually forms on the lips and is always outside the mouth.⁹ Cold sores are caused by a common viral infection: the herpes simplex virus, usually the subtype HSV-1.¹⁰ If someone has a cold sore, over-the-counter products like Abreva Docosanol 10% Cream 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 it to go away completely.¹¹ One to two weeks is typical, says Dr. Stone, larger canker sores can last as long as four weeks.^12, 13

Are canker sores contagious? 

Unlike cold sores, which are caused by the highly contagious herpes simplex virus, canker sores are not contagious; they can’t be spread to other people.¹⁵

How to find symptom relief support for a canker sore

At-home remedies for canker sores

Consider 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 the mouth before spitting it out.^16, 17

Avoid foods that might irritate the inflamed mouth more, including very acidic or salty foods, alcohol, fizzy drinks and hard foods like crisp breads. Soups and soft foods might be more comfortable. Keep food temperatures cool or warm.¹⁸

Relief support products for canker sores

If the canker sore isn’t too bothersome, a pain reliever may not be needed. But for those in pain, some products may help reduce the discomfort.¹⁹ Gels or creams that contain benzocaine, a topical numbing agent, may help reduce pain.^20, 21 Products that cover the sore to prevent biting on it can help as well.

A health care provider might prescribe a mouthwash with a germ-killing ingredient like chlorhexidine.²² But be sure to avoid alcohol-based rinses that might aggravate pain.²³

When to see a health care provider about a canker sore

If at-home treatments don’t help or if the pain gets in the way of daily life, see a health care provider.²⁴ They may prescribe a steroid (in pill or cream form) or cauterize the inflamed tissue with silver nitrate or lasers.^25, 26

Also seek medical care if the canker sore is unusually large (one centimeter or larger in diameter), if more than a few appear at one time or if the canker sore doesn’t resolve over a couple of weeks.^27, 28

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