Stomatitis is a condition involving inflammation of the tissue that lines the inside of your mouth. This inflammation can show up as painful sores, swelling, or redness anywhere inside your mouth, including on your gums, tongue, lips, or cheeks, making everyday activities like eating, drinking, or talking uncomfortable for many people.

Understanding Stomatitis and Its Prevalence

Stomatitis is a general term used to describe inflammation or swelling in the mucous membranes (the thin, moist skin) that line the inside of your mouth and lips. This inflammation is your body’s natural response when something damages these delicate tissues. The condition can range from a minor nuisance that heals on its own to a more serious problem requiring medical care. Understanding stomatitis means recognizing that it isn’t just one single disease, but rather a group of conditions that share the common feature of mouth inflammation.^[1]

The prevalence of stomatitis varies depending on the specific type. The most common form, known as recurrent aphthous stomatitis (canker sores), affects roughly 5 to 25 percent of people in the United States at some point in their lives. Some sources suggest that about 20 percent of the general population experiences this condition to some degree.^[2][4][5] This makes it one of the most common diseases affecting the mouth area. While stomatitis can occur in anyone, certain types are more common in specific age groups or populations.

When it comes to demographics, canker sores tend to appear more often in young people, particularly those between 10 and 19 years of age. Women experience canker sores more frequently than men.^[2][4] Cold sores caused by the herpes virus, another common type of stomatitis, typically first appear in young children between 6 months and 5 years old, though the virus can stay dormant in the body and cause outbreaks later in life.^[7] For patients undergoing cancer treatment, stomatitis is particularly common. Approximately 20 to 40 percent of people receiving chemotherapy develop this condition, and the percentage climbs even higher—over 70 percent—for those undergoing bone marrow transplants.^[12][16]

What Causes Stomatitis

Stomatitis can develop from numerous causes, and often multiple factors work together to trigger the condition. The most straightforward explanation is that anything damaging the delicate lining inside your mouth can lead to inflammation. Because your body responds to injury by sending blood and immune cells to the damaged area, this creates the redness, swelling, and pain characteristic of stomatitis.^[1]

Infections represent one of the major causes of stomatitis. The most common infectious culprit is HSV-1 (herpes simplex virus type 1), which causes cold sores. This virus is highly contagious and, once contracted, remains in the body for life, potentially causing recurring outbreaks. Other viral infections, including chickenpox, shingles, and infections from viruses like Epstein-Barr or cytomegalovirus, can also lead to mouth inflammation.^[1][2][3] Bacterial infections, often related to poor oral hygiene or gum disease, can trigger stomatitis as well. Fungal infections, particularly an overgrowth of Candida fungi (causing thrush), represent another infectious pathway to developing stomatitis.^[3]

Physical injuries to the mouth are another common cause. These injuries can come from many sources: accidentally biting the inside of your cheek or tongue, scraping from ill-fitting dentures or braces, sharp edges on broken teeth, or burns from hot food and drinks. Even vigorous tooth brushing can sometimes damage the delicate mouth tissues enough to cause inflammation.^[1][2]

Allergic reactions and irritation from certain substances also play a role. Some people develop stomatitis in response to ingredients in dental products like toothpaste (particularly sodium lauryl sulfate), mouthwash, or even components in cosmetics like lipstick. Certain foods, especially spicy dishes, acidic fruits, or specific items like chocolate, coffee, nuts, cheese, and tomatoes, can trigger mouth inflammation in susceptible individuals.^[2][3][9] Tobacco use, whether smoking or chewing, is also a well-recognized cause of stomatitis.^[2]

Medical treatments, particularly for cancer, frequently cause stomatitis as a side effect. Chemotherapy and radiation therapy work by killing rapidly dividing cancer cells, but they also damage other fast-growing cells in the body, including those lining the mouth. This makes the mouth vulnerable to inflammation and sores during cancer treatment.^[1][12] Certain medications, including some antibiotics, anti-seizure drugs, and medications for rheumatoid arthritis, have also been associated with causing stomatitis.^[2][3]

Systemic diseases and nutritional deficiencies round out the causes. Autoimmune conditions like lupus, Crohn’s disease, Behçet’s disease, and celiac disease can all manifest with mouth inflammation.^[2][3] Deficiencies in essential nutrients—particularly iron, vitamin B12, folate (vitamin B9), or zinc—can lead to stomatitis because these nutrients are necessary for healthy cell growth and repair in the mouth.^[3][5] A weakened immune system, whether from HIV/AIDS, illness, or simply being run down, also increases susceptibility to developing mouth inflammation.

Risk Factors for Developing Stomatitis

Certain groups of people and specific behaviors increase the likelihood of developing stomatitis. Understanding these risk factors can help identify who might be more vulnerable to this condition and why prevention efforts are particularly important for these individuals.

People undergoing cancer treatment face significantly elevated risk. As mentioned earlier, chemotherapy patients have a 20 to 40 percent chance of developing stomatitis, while those receiving radiation therapy to the head and neck area have an even higher likelihood. The combination of chemotherapy and radiation compounds this risk further.^[12][16]

Age plays a role in determining risk for different types of stomatitis. Young children are more susceptible to initial infections with the herpes simplex virus, which causes cold sores. Meanwhile, canker sores most commonly affect adolescents and young adults, particularly those in their teens and twenties.^[4][7] Older adults who wear dentures face increased risk of developing denture-related stomatitis, especially if the dentures don’t fit properly or aren’t cleaned adequately.

Genetic factors and family history matter as well. Canker sores often run in families, suggesting a genetic predisposition to this condition. If your parents experienced frequent canker sores, you’re more likely to develop them too.^[2]

Lifestyle factors significantly influence risk. Tobacco users—whether they smoke cigarettes, pipes, or use chewing tobacco—are at higher risk for developing nicotine stomatitis and other forms of mouth inflammation. Poor oral hygiene creates an environment where bacteria can thrive, increasing the likelihood of infections that lead to stomatitis.^[2] People who experience high levels of stress or don’t get adequate sleep may find themselves more prone to canker sore outbreaks.^[2][9]

Certain underlying health conditions increase vulnerability. People with autoimmune diseases, inflammatory bowel disease, celiac disease, or immunocompromised states (like HIV/AIDS) face elevated risk. Women may be more susceptible than men, particularly during times of hormonal changes such as menstruation.^[2][3]

Recognizing the Symptoms

The symptoms of stomatitis can vary depending on what’s causing the inflammation and which type you have, but certain signs are common across most forms. Recognizing these symptoms early allows for quicker treatment and relief.

Pain and discomfort are hallmark symptoms of stomatitis. The pain can range from mild irritation to severe discomfort that interferes with eating, drinking, talking, or swallowing. Many people describe a burning sensation on the tongue or roof of the mouth. This pain often intensifies when consuming certain foods or beverages, particularly those that are hot, spicy, salty, or acidic.^[1][6]

Visual changes inside the mouth are another key indicator. You might notice redness and swelling of the tissues lining your mouth. Depending on the type of stomatitis, you may see one or more sores or ulcers. Canker sores typically appear as round or oval spots with a white, gray, or yellow center and a red border. They usually develop on soft tissues like the inside of the lips or cheeks, on the tongue, or on the floor of the mouth.^[1][2] Cold sores, on the other hand, begin as fluid-filled blisters that appear alone or in clusters on or around the lips. Before the blisters appear, you might feel tingling, tenderness, or burning in the area. Eventually, these blisters crust over with a scab.^[2]

Some types of stomatitis cause white or gray patches to form on the tongue, the roof of the mouth, or inside the cheeks. This is particularly common with fungal infections like thrush.^[1]

Functional difficulties often accompany the physical symptoms. The pain and inflammation can make it hard to eat and drink normally, which can lead to unintended weight loss, dehydration, or malnutrition if the condition persists. Speaking clearly may become challenging, and some people experience increased drooling. Swollen gums are common, and bleeding from the gums or mouth sores may occur.^[6][16]

In some cases, especially with infections like herpetic stomatitis, systemic symptoms may develop. These can include fever, swollen lymph nodes in the neck, and a general feeling of being unwell or run down. Cold sores are sometimes associated with flu-like symptoms.^[2][7]

The duration of symptoms varies by type. Canker sores typically last between 5 to 10 days in minor cases, though larger, more severe sores can persist for several weeks. Cold sores usually resolve within 7 to 10 days. Both types have a tendency to recur, meaning you might experience multiple episodes over time.^[2][9]

Prevention Strategies

While not all cases of stomatitis can be prevented—particularly those caused by viral infections you’ve already been exposed to or those resulting from necessary medical treatments—many strategies can reduce your risk or minimize the severity of outbreaks.

Maintaining excellent oral hygiene is the foundation of prevention. Brushing your teeth at least twice daily with a soft-bristled toothbrush helps remove bacteria that can lead to infections. Flossing daily cleans between teeth where your toothbrush can’t reach. Using gentle brushing techniques prevents trauma to the delicate tissues in your mouth. Some people find that switching to a toothpaste without sodium lauryl sulfate, a common irritant, helps reduce canker sore outbreaks.^[2][6]

Regular dental checkups play a crucial role in prevention. Your dentist can identify and address potential problems before they lead to stomatitis. This includes fixing broken or jagged teeth that might scrape the inside of your mouth, adjusting ill-fitting dentures or braces, and treating gum disease early. For people about to undergo cancer treatment, seeing a dentist beforehand to address any oral health issues can significantly reduce the risk of developing treatment-related stomatitis.^[12][16]

Dietary considerations can help prevent stomatitis in susceptible individuals. If you notice that certain foods trigger mouth sores, avoiding those items makes sense. Common culprits include acidic foods like citrus fruits and tomatoes, spicy foods, and specific items like chocolate, coffee, nuts, and cheese. Ensuring adequate nutrition is equally important—eating a balanced diet rich in vitamins and minerals supports healthy mouth tissues and immune function.^[2][6][9]

Lifestyle modifications can reduce your risk. If you use tobacco, quitting is one of the most effective preventive measures. Tobacco not only causes direct irritation to mouth tissues but also impairs healing. Managing stress through relaxation techniques, adequate sleep, and healthy coping strategies may help reduce outbreaks of canker sores, which are often triggered by stress.^[2]

For cold sores caused by the herpes virus, specific prevention strategies apply. Since the virus spreads through direct contact, avoiding kissing or sharing utensils, lip balm, or other personal items with someone who has an active cold sore helps prevent initial infection. For those who already have the virus, identifying and avoiding personal triggers—such as excessive sun exposure, stress, fever, or hormonal changes—can help prevent outbreaks. Using lip balm with sunscreen may reduce sun-triggered episodes.^[2]

Being mindful of potential allergic triggers also helps. If you’ve noticed reactions to certain cosmetics, dental products, or other substances that contact your mouth, switching to alternatives can prevent allergic stomatitis. Reading product labels and choosing items free from known irritants makes a difference for sensitive individuals.

For people with underlying health conditions that increase stomatitis risk, working closely with healthcare providers to manage those conditions effectively serves as an important preventive strategy. This might include controlling diabetes, managing inflammatory bowel disease, or addressing nutritional deficiencies through supplementation when needed.

How Stomatitis Affects the Body

Understanding the changes that occur in your body during stomatitis helps explain why the condition causes the symptoms it does and why proper care is important. The process begins at the cellular level when something damages the epithelial cells (the cells making up the lining of your mouth).

The mucous membranes lining your mouth are normally smooth, moist, and pink. These tissues are made up of rapidly dividing cells that constantly renew themselves—in fact, the cells lining your mouth replace themselves every few days. This rapid turnover is generally beneficial because it allows the mouth to heal quickly from minor injuries. However, this same characteristic makes these cells vulnerable to things that interfere with cell division, such as chemotherapy drugs.^[12]

When injury or infection occurs, your body’s immune system responds by triggering inflammation. Blood vessels in the affected area dilate (widen), which increases blood flow to the region. This explains the redness you see. The increased blood flow brings immune cells to fight infection and begin the healing process. Fluid also leaks from these blood vessels into the surrounding tissues, causing swelling. The swollen tissues press on nerve endings, creating the pain and sensitivity characteristic of stomatitis.^[1]

In cases where ulcers or sores form, the protective surface layer of the mucous membrane has broken down, exposing the deeper, more sensitive tissues underneath. This is why even mild stimuli like food, drinks, or simply talking can cause significant pain—the nerve endings that are normally protected by the surface layer are now exposed to direct contact.^[9]

When infection is the cause, the pathogen itself contributes to tissue damage. The herpes simplex virus, for example, invades cells and uses their machinery to replicate. As new viral particles burst out of infected cells to spread to neighboring cells, this destroys the host cells and creates the characteristic blisters. Bacterial infections trigger an immune response that, while fighting the bacteria, can also damage surrounding healthy tissue. Fungal infections like thrush create patches where the fungus has overgrown, disrupting the normal balance of microorganisms in the mouth.^[3]

Normal saliva production and flow play a protective role in mouth health. Saliva contains substances that fight bacteria and helps wash away food particles and debris. It also keeps the mouth moist, protecting the mucous membranes from drying out. When something reduces saliva production—a condition called xerostomia or dry mouth—the mouth becomes more vulnerable to stomatitis of any cause. This is why medications or treatments that decrease saliva production increase stomatitis risk.^[3][13]

In cancer treatment-related stomatitis, the mechanisms are particularly clear. Chemotherapy drugs and radiation therapy target rapidly dividing cells because cancer cells divide quickly. Unfortunately, the cells lining the mouth also divide rapidly, making them “collateral damage” in the fight against cancer. The damaged mouth lining becomes thin and fragile, breaks down more easily, and doesn’t repair itself as quickly as normal. This creates the painful ulcerations and inflammation seen in cancer patients.^[12]

The functional impairments from stomatitis extend beyond just local discomfort. When eating and drinking become painful, people naturally consume less, which can lead to dehydration and inadequate nutrition. This is particularly concerning in vulnerable populations like cancer patients or elderly individuals who may already be at nutritional risk. Difficulty swallowing might cause people to avoid necessary medications. In severe cases, especially in people with weakened immune systems, bacteria from mouth sores can enter the bloodstream and cause more serious systemic infections.^[3][16]