Stomatitis: Causes, Symptoms, and How to Treat Mouth Inflammation

What Is Stomatitis (Mouth Inflammation)?

Stomatitis is inflammation of the lining of your mouth, lips, gums, or tongue. Some forms cause visible ulcers, while others show up as red, swollen, or sore patches without open sores.² The term covers a wide range of conditions, from common canker sores to denture-related thrush.

Stomatitis Quick Facts

• What is stomatitis? — Inflammation of the lining of the mouth, lips, gums, or tongue — sometimes with ulcers, sometimes without.²
• What causes it? — Infections (viral, bacterial, fungal), nutrient deficiencies, allergies, stress, chronic illness, and cancer treatment.^1,2
• What are the most common types? — Canker sores (recurrent aphthous stomatitis), cold sores (herpetic stomatitis), denture stomatitis, and angular cheilitis.^1,2
• How is it treated? — Treatment targets the cause: topical pain relief for sores, antifungals or antivirals for infections, and supplements for nutrient gaps.^2,4

Common Symptoms of Stomatitis

The hallmark symptoms are pain and visible changes in the soft tissue of your mouth. Most cases include one or more of the following:

• Painful soreness in your cheeks, lips, tongue, or roof of the mouth
• Visible sores (ulcers), red patches, or white patches
• Pain when chewing, brushing, or swallowing

Depending on the cause, you may also notice a headache, fever, or general malaise. Symptoms that last longer than two weeks, or that come with fever and trouble eating, are worth a call to your dentist or doctor.²

Types of Stomatitis

Most stomatitis falls into one of a handful of recognized types. Identifying the type helps narrow down the cause and the right treatment.

Recurrent Aphthous Stomatitis (Canker Sores)

Canker sores are small, round ulcers with a white or yellow center and a red border that appear on the inner cheeks, lips, or tongue.^3,4 They typically heal on their own within seven to ten days but recur in roughly 20% of adults. The exact cause isn’t clear — current evidence points to a combination of immune response, nutrient deficiencies, stress, and minor mouth trauma — and there’s no permanent cure.^1,4 Treatment focuses on pain relief with topical gels, rinses, and managing triggers like spicy or acidic foods. See our deep dive on canker sores for the full picture.

Herpetic Stomatitis (Cold Sores)

Herpetic stomatitis is usually caused by herpes simplex virus type 1 (HSV-1), the strain most often linked to oral herpes.^5,21 The first infection — primary herpetic gingivostomatitis — usually hits young children and produces widespread mouth ulcers, swollen gums, fever, and trouble eating.⁵ After that initial illness, the virus stays dormant in nerve tissue and reactivates as cold sores around the lips, typically triggered by stress, illness, sun exposure, or fatigue.^5,21 Antiviral medications shorten outbreaks when started early.

Denture-Related Stomatitis

Denture stomatitis is red, inflamed tissue under a removable denture, especially an upper denture.⁶ It’s most commonly tied to Candida overgrowth, but poor denture hygiene, an ill-fitting denture, and wearing dentures around the clock all contribute.^6,7 Treatment combines antifungal medication (oral thrush treatment) with better denture cleaning and giving your gums a break overnight.

Angular Cheilitis

Angular cheilitis causes red, cracked, sometimes crusty sores at the corners of the mouth.⁸ Common triggers include drooling, ill-fitting dentures, lip-licking, vitamin deficiencies, and yeast or bacterial infection in moist skin folds. It usually resolves with topical antifungal or antibacterial creams plus a barrier ointment to keep the corners dry.

Geographic Tongue (Migratory Stomatitis)

Geographic tongue is a benign condition with smooth, red patches surrounded by white borders that change shape and location over days or weeks.⁹ See our geographic tongue page for more. The cause isn’t fully understood, and most people have no symptoms. When the patches sting from spicy or acidic foods, a topical anesthetic or anti-inflammatory rinse helps.

Allergic (Contact) Stomatitis

Contact stomatitis is mouth inflammation triggered by an allergen — most commonly cinnamon flavoring, peppermint, certain metals (like nickel), and ingredients in toothpaste or mouthwash.¹² The lining looks red, swollen, and tender, and sometimes peels or cracks. Identifying and avoiding the trigger usually clears it within a week or two.

Necrotizing Stomatitis

Necrotizing stomatitis sits on a spectrum that includes trench mouth (necrotizing ulcerative gingivitis) and cancrum oris.¹⁰ Tissue death, severe pain, bleeding, a foul smell, and fever set it apart from milder forms of gum inflammation. It tends to occur in people with weakened immune systems and needs urgent dental care, antibiotics, and aggressive cleaning.

Six Potential Causes of Stomatitis

1. Nutritional Deficiencies

Low iron or ferritin, folate, and vitamin B12 are the nutrient gaps most consistently linked to recurrent mouth ulcers.¹³ Other B vitamins are sometimes implicated, but the evidence is strongest for those three. Zinc has shown promise too: a 2021 systematic review found zinc supplementation reduced ulcer frequency in some patients with recurrent canker sores.¹⁴

You’re more likely to develop a deficiency-related stomatitis if you have:

• A restrictive diet that’s low in these nutrients
• An underlying condition that interferes with absorption (celiac disease, inflammatory bowel disease, gastric bypass)

A blood test confirms the deficiency, and most cases respond well to dietary changes or supplements.

2. Allergies or Irritation

Cinnamon flavoring, peppermint oil, and metals like nickel are the most common allergic triggers for mouth inflammation.¹² The lining turns red, swells, peels, or stings within hours of exposure to a toothpaste, mouthwash, chewing gum, or candy that contains the trigger.

Nicotine stomatitis is a separate, smoking-related form. It shows up as a painless white patch on the roof of the mouth from repeated heat exposure, especially in pipe and cigar smokers, and typically reverses when smoking stops.¹¹

3. Infections

Viral, bacterial, and fungal infections are the most frequent infectious causes of stomatitis. HSV-1 causes oral herpes and cold sores in roughly half of U.S. adults under 50.²¹ Candida overgrowth drives most denture-related stomatitis and thrush.⁷ Bacterial infections typically follow poor oral hygiene or trauma.

HIV weakens the immune system and raises the risk of several oral conditions, including mouth ulcers, oral thrush (white patches that scrape off to reveal raw, red tissue underneath), non-wipeable white patches like oral hairy leukoplakia, and necrotizing forms of stomatitis.²² Anyone with persistent or unusually severe mouth infections should be evaluated for an underlying immune issue.

4. Stress

Stress is a well-documented trigger for both canker sores and cold sore outbreaks. One study of dental and medical students found significantly higher psychological stress scores in those with recurring canker sores.¹⁵ The mechanisms differ: aphthous ulcers flare from stress-related immune dysregulation, while stress reactivates the latent herpes virus behind cold sores.⁵

Better sleep, regular exercise, and the same stress-management habits that help anxiety and skin conditions may also lower flare frequency for some people.¹

5. Chronic Illnesses

Several systemic conditions can contribute to stomatitis, including diabetes, Crohn’s disease, celiac disease, HIV-related immune suppression, Behçet disease, and nutritional deficiencies.^1,2,16,17,22 People with diabetes who wear dentures are roughly twice as likely to develop denture-related Candida infection as people without diabetes.¹⁷ Crohn’s disease also causes pyostomatitis vegetans, a distinctive pattern of yellow pustules and ulcers in the mouth that sometimes appears before any gut symptoms.¹⁶

Better control of the underlying condition usually improves the oral symptoms.

6. Cancer Treatment and Other Medications

Oral mucositis affects 20% to 40% of patients on standard-dose chemotherapy and the majority of patients receiving head and neck radiation or high-dose conditioning regimens for stem cell transplant.^18,19 Pain is severe enough to interfere with eating, and the condition is closely related to stomatitis. Clinicians sometimes distinguish the two — mucositis affects mucous membranes throughout the digestive tract, while stomatitis usually refers to the mouth.¹⁸

Cancer teams use mouth rinses, cryotherapy (sucking ice chips during certain infusions), pain control, and meticulous oral hygiene to limit the damage. Certain antibiotics, NSAIDs, and other medications also trigger oral ulcerations as a side effect.²⁰

How Is Stomatitis Diagnosed?

A dentist or doctor diagnoses stomatitis with a physical exam and a careful history. Canker sores, cold sores, and angular cheilitis have a recognizable appearance and pattern.²

Expect questions about diet, stress, medications, recent illnesses, and your dental and medical history. When the cause isn’t obvious — or when ulcers are unusually large, persistent, or recurring — the next step is blood work for nutrient deficiencies and immune markers, a swab for infection, or a tissue biopsy.

How to Treat Stomatitis

Treatment depends on the type and cause. A typical plan draws from one or more of these:

• Topical medications (anesthetic gels, corticosteroid pastes) for canker sores and contact stomatitis
• Antivirals for HSV-related cold sores and gingivostomatitis⁵
• Antifungals for denture stomatitis and oral thrush⁶
• Antibiotics for bacterial infections and necrotizing forms¹⁰
• Iron, folate, B12, or zinc supplementation when a deficiency is confirmed^13,14
• Better oral hygiene and denture care
• Stress management for recurrent canker sores and HSV outbreaks

Mild canker sores and cold sores usually clear within one to two weeks once the trigger is addressed.²³ Infections, denture stomatitis, cancer-treatment mucositis, necrotizing disease, and recurrent ulcers tied to a systemic cause need targeted treatment and follow-up before they settle down.¹⁸

Can a Dentist Treat Stomatitis?

Yes — a dentist diagnoses and treats most common types. Causes that need broader medical care, like a nutrient deficiency tied to absorption, Crohn’s disease, or HIV, also involve your primary care doctor or a specialist.

If you notice an unusual change in the look or feel of your mouth, your dentist is a good first stop.

How to Prevent Stomatitis

Not every cause is preventable, but a few habits lower the risk of mouth ulcers and inflammation:

• Brush twice a day with a soft-bristled toothbrush and floss daily
• Eat a balanced diet with enough iron, B vitamins, and zinc
• Get regular exercise and consistent sleep to support immune function
• Avoid foods that irritate you — common culprits include very hot, spicy, acidic, or rough-textured foods
• Skip toothpastes and mouthwashes that contain ingredients you react to (cinnamon and strong mint flavorings are common triggers)
• Quit or cut back on tobacco
• Clean removable dentures daily and leave them out overnight when possible
• Stay current with care for any chronic health conditions

When to See a Dentist or Doctor

Most mouth sores clear up on their own. A few patterns deserve prompt professional attention:

• Sores that don’t heal within two weeks — Persistent ulcers, red patches, or white patches are early warning signs of oral cancer and need an in-person exam.²⁴
• Fever plus widespread mouth ulcers in a young child — This combination can signal primary herpetic gingivostomatitis or another childhood viral illness like hand-foot-and-mouth disease, and it risks dehydration if eating and drinking become too painful.⁵
• A white patch that doesn’t wipe off — Patches that scrape off are usually thrush, while patches that don’t wipe off (such as leukoplakia) need a closer look.²²
• Severe pain, gum bleeding, a foul smell, and fever — Especially in someone with a weakened immune system, this combination points to necrotizing periodontal disease and needs same-day care.¹⁰
• Recurring mouth ulcers with gut symptoms — Frequent ulcers paired with diarrhea, abdominal pain, or unexplained weight loss are sometimes the first clue to Crohn’s disease.¹⁶

When in doubt, a quick visit is the right call. Your dentist will confirm a benign cause, treat the most common forms on the spot, and refer you on if something else is going on.²⁵