Canker Sores and Mouth Ulcers: Causes, Relief and When a Sore Needs a Visit

What it involves

MedlinePlus describes a canker sore as a painful open sore in the mouth, white or yellow with a bright red border. Canker sores are not cancerous and are not the same as a fever blister, which is a cold sore. They are a common type of mouth ulcer, and they most often appear on the inside of the cheeks and lips, the tongue, or the gum base.

Who this is for

• Patients with painful white or yellow mouth sores that make eating and drinking difficult
• Patients who get canker sores more than two or three times a year
• Patients with a mouth sore that has not healed after two weeks of home care
• Patients whose mouth sores come with fever, diarrhea, headache, or a skin rash

What to expect

• Questions about where the sores are, how often they return, and what you were eating or doing before
• A look inside the mouth, since MedlinePlus says a provider can often tell by looking
• A review of diet, vitamins, and medicines, plus blood work if a deficiency or other cause is suspected
• A plan that may include comfort measures, a prescribed rinse or medicine, or a referral for a sore that is not healing

What triggers them

MedlinePlus says the cause is sometimes unknown, but canker sores can follow viral infections, immune system problems, and small injuries from dental work, rough brushing, or biting the cheek or tongue. It also names emotional stress, hormone changes, food allergies, and a shortage of iron, folic acid, or vitamin B12. Canker sores are more common in women and can run in families.

How they feel and how long they last

A canker sore starts as a painful red bump that opens into an ulcer with a white or yellow center, usually under a third of an inch across. MedlinePlus says healing begins with a gray color, pain often fades in 7 to 10 days, and a complete cure takes one to three weeks, longer for large ulcers. Fever, swollen glands, or a general unwell feeling are less common.

Easing the pain at home

MedlinePlus lists several steps for comfort:

• Skip hot, spicy, and salty foods while the sore is raw
• Rinse with salt water or a mild mouthwash that contains no alcohol
• Use an over-the-counter numbing rinse or drops for short relief
• Brush twice a day, floss, and keep up routine dental checkups

What a provider may add

For severe cases, MedlinePlus says a provider may prescribe a chlorhexidine mouthwash or a stronger corticosteroid applied to the sore or taken by mouth. In some people, acid-reducing medicines help. Vitamin levels can be checked with blood work, as the vitamin D and B12 testing guide and anemia and low iron guide explain.

When a mouth sore is not a canker sore

MedlinePlus says that if sores persist or keep coming back, a provider looks for other causes such as medicine allergies, a herpes infection, and conditions like erythema multiforme or lichen planus. It stresses that canker sores do not cause cancer, but certain cancers first appear as a mouth ulcer that does not heal, which is the reason a lingering sore should be checked. A sore with blisters on the lip is usually a cold sore, covered in the cold sores guide.

When to book

MedlinePlus advises contacting a provider when a mouth ulcer does not go away after two weeks of home care or gets worse, when canker sores come back more than two or three times a year, or when they come with fever, diarrhea, headache, or a rash. A fever with a sore throat may point somewhere else, as the sore throat guide describes.

Sources

• MedlinePlus — Canker sore
• MedlinePlus — Canker Sores health topic