Giant Canker Sore — What Is a Major Aphthous Ulcer?

TL;DR

A "giant" canker sore is what doctors call a major aphthous ulcer: a canker sore wider than about 1 cm (10 mm). Compared with ordinary canker sores, they're deeper, much more painful, take anywhere from two to six weeks or longer to heal, and often leave a scar (Edgar et al., 2017 — J Clin Aesthet Dermatol). Most canker sores, around 80%, are the ordinary minor kind; major ones are much less common. Because they're more often linked to an underlying condition, a first major ulcer is a good reason to get blood work and, depending on your risk factors, an HIV test. Over-the-counter patches and gels help with pain but won't speed healing. The main treatment is a prescription steroid, applied to the sore, injected into it, or occasionally taken by mouth for a short course. People who get major ulcers over and over may need a specialist and a daily preventive medication. Any mouth ulcer that hasn't clearly improved after three weeks should be checked, though with a major ulcer, steady improvement over several weeks can be normal.

What Makes It "Major"

Doctors divide canker sores into three types:

(Edgar et al., 2017 — J Clin Aesthet Dermatol)

To get a sense of the size: 1 cm is about the width of a pencil eraser. Major sores can be considerably bigger than that, sometimes covering a good part of the inside of a lip or cheek.

It isn't just size. Ordinary canker sores are shallow. Major ones go deeper into the tissue under the lining of the mouth. That depth explains the three things that make them miserable: more pain, slower healing, and scarring. Major canker sores also tend to show up further back in the mouth, including the soft palate and the area around the tonsils, where they can make swallowing painful. Some people get one major sore at a time; others get several, or get major and minor sores together.

The older medical name for repeated major canker sores is Sutton's disease.

Why They're So Hard to Live With

The pain

A major canker sore can make eating, drinking, talking, and swallowing genuinely painful for a week or more. It's not unusual for people to lose weight during a bad one because eating hurts too much. Unlike an ordinary sore that becomes tolerable after a few days, a major sore can stay acutely painful for a long time before it starts to settle.

The time

Two to six weeks is a long time to have an open wound in your mouth. People who get major sores repeatedly sometimes have only a few sore-free weeks between them, or none.

Scarring

Because they're deep, major canker sores often heal with a scar: a pale, slightly firm patch where the sore was. The scar itself is harmless, but repeated sores in the same area can leave the tissue tight or uneven.

Get Checked After Your First One

Ordinary canker sores in otherwise healthy people are usually tied to everyday triggers: SLS in toothpaste, minor injuries, stress, and nutrient gaps. Major canker sores can come from the same triggers, but they're more often linked to an underlying condition. A first major ulcer, especially if you've never had canker sores before or you're over 30 when it starts, is a good reason to look further.

Conditions linked to major canker sores include:

• Iron, B12, folate, or zinc deficiency. See B12 for Canker Sores and Iron Deficiency and Canker Sores.
• Celiac disease. Keep eating gluten until you've been tested. See Gluten and Canker Sores.
• Crohn's disease and ulcerative colitis. See Canker Sores and Crohn's Disease.
• HIV. Major canker sores are more common in people with HIV, especially when the immune system is significantly weakened, and can be a sign the infection is progressing. If you have any risk factors, or have never been tested, an HIV test is reasonable. See Canker Sores in HIV and Immunocompromised People.
• Behçet's disease, especially if you also get genital sores, eye inflammation, or skin problems. See Canker Sores and Behçet's Disease.
• Low white blood cell counts (neutropenia), from chemotherapy, some medications, or a blood condition.

Tests worth asking for: a complete blood count, ferritin, vitamin B12, folate, zinc, a celiac screen (tissue transglutaminase IgA), and an HIV test if appropriate. Depending on your other symptoms, your doctor may add inflammatory markers or a referral. See When to See a Doctor for a Canker Sore.

Treatment

Over-the-counter products help with pain but don't change how long a major sore lasts. Prescription treatment does more. For a full ranking of options, see How to Get Rid of a Canker Sore Fast.

Steroids applied to the sore

This is the first-line treatment. A dentist or doctor prescribes a steroid gel, paste, or rinse that you apply to the sore several times a day. Topical steroids reduce pain and help canker sores heal faster than placebo (systematic review, 2008 — PMID: 18588791), and reduce how severe they get, though they don't stop new ones from forming (Scully & Porter, 2008 — PMID: 17850936). For a major sore, your prescriber may choose a stronger steroid than the ones used for ordinary canker sores. They work best started as early as possible.

The practical problem with a big sore is keeping the medicine on it. Applying it after meals and at bedtime, when your mouth will be still for a while, and not eating or drinking for about 30 minutes afterward, helps.

A steroid injection into the sore

For a single large, very painful sore, some dentists and oral medicine specialists inject a small amount of steroid directly into or around it. It's done with a local anesthetic, and it can be a good option when a topical steroid can't stay in contact with the sore. The evidence for this comes mainly from clinical experience rather than trials.

A short course of oral steroids

When major sores are severe, numerous, far back in the mouth, or stopping you from eating, a doctor may prescribe a short course of steroid tablets. They usually work quickly. Steroids taken by mouth have more side effects than topical ones, so they're used for bad flare-ups rather than routinely, and the dose and schedule should come from your prescriber.

Chemical cautery and laser at the dentist

Debacterol, a chemical applied in the office that seals the surface of the ulcer, usually brings fast pain relief. With a large sore, covering the whole surface evenly is harder, so it's worth having it done by a dentist experienced with it. The evidence is stronger for pain relief than for faster healing. Laser therapy is another option some dentists offer, and it may take several sessions for a large sore. Silver nitrate is a third cautery option, but it can leave permanent gray-black staining, and given the choice we'd recommend Debacterol over it. See Silver Nitrate for Canker Sores.

Preventive medication for frequent major sores

For people who get major sores again and again, a specialist may suggest a daily medication to reduce how often they come. None of these is proven to work for everyone. A Cochrane review of medications taken by mouth for recurring canker sores couldn't identify a single one with clearly proven effectiveness (Brocklehurst et al., 2012 — Cochrane Database Syst Rev). Options a specialist may consider include:

• Colchicine, an anti-inflammatory drug. In a small trial of 34 people, colchicine and a low dose of prednisolone worked about equally well over three months, but colchicine had far fewer side effects. See How to Get Rid of a Canker Sore Fast.
• Dapsone, which has shown benefit in small open studies (Mimura et al., 2009 — Clinics).
• Pentoxifylline, which had only a modest effect in a small placebo-controlled trial (Thornhill et al., 2007 — Arch Dermatol).
• Apremilast, which significantly reduced mouth ulcers in a large trial of people with Behçet's disease (Hatemi et al., 2019 — PMID: 31722152). It's approved for Behçet's mouth ulcers, not ordinary canker sores.
• Thalidomide, which is very effective for severe mouth ulcers. In people with HIV, 55% of major canker sores healed completely within four weeks on thalidomide, compared with 7% on placebo (Jacobson et al., 1997 — N Engl J Med). It causes severe birth defects and nerve damage, so it's tightly restricted and reserved for the most severe cases.

These are specialist decisions. An oral medicine specialist or a dermatologist with experience in mouth ulcers is the right person to see.

Pain relief while it heals

• Barrier patches protect the sore. A large sore may need more than one, and they're harder to keep in place.
• Film-forming liquids like Kanka cover irregular sores better than patches.
• Numbing gels before meals.
• Pain relievers by mouth, such as acetaminophen or ibuprofen, help with the background ache.
• Soft, bland food for the duration. Skip anything hard, sharp, acidic, salty, or spicy.
• Keep drinking. Cool liquids and a straw can help.

When a Major Sore Needs a Second Look

Any mouth ulcer that hasn't clearly improved after three weeks should be checked. With a major canker sore, steady improvement over several weeks can be normal, so what matters is the direction it's heading:

• Getting smaller, less painful, edges filling in: on track, even at three or four weeks.
• The same size, getting bigger, doesn't hurt, or has a hard edge: needs to be looked at now. A biopsy may be needed to rule out other causes, including cancer.

See Canker Sore Won't Heal for what a non-healing sore can be and what a biopsy involves.