Most sores on the gums are canker sores (aphthous ulcers) or minor injuries from rough foods, aggressive brushing, or dental work. These are the most common causes and typically heal on their own within one to two weeks. But gum sores can also signal infections, nutritional gaps, autoimmune conditions, or, rarely, something more serious like oral cancer.
Canker Sores
Canker sores are small, shallow ulcers that form on soft tissues inside the mouth, including the gums. They’re not contagious and aren’t caused by a virus. Instead, they tend to be triggered by a combination of factors: emotional stress, a minor mouth injury (like biting your cheek or poking your gum with a chip), hormonal shifts, or a diet low in certain nutrients. Deficiencies in vitamin B-12, iron, zinc, and folate are all recognized triggers.
In some people, canker sores recur because the immune system mistakenly attacks healthy cells in the mouth lining instead of actual pathogens. Conditions that suppress the immune system, like HIV/AIDS, also increase the frequency and severity of outbreaks. Most canker sores are painful for a few days but resolve within 7 to 14 days without treatment.
Physical Injury and Irritation
Your gum tissue is surprisingly easy to damage. Hard or sharp foods like tortilla chips, crusty bread, or popcorn kernels can scrape the gums and leave a sore spot. Brushing too hard, using a toothbrush with stiff bristles, or flossing aggressively can do the same thing. Ill-fitting dentures, braces, or retainers that rub against the gums are another frequent culprit.
Burns from hot food or drinks can also cause sores that look alarming but are simply thermal injuries. These typically heal within a week or two once the source of irritation is removed.
Viral Infections
The herpes simplex virus can cause a condition called gingivostomatitis, which produces painful sores on the lips, gums, tongue, and inner cheeks along with red, tender, swollen gums. This is especially common in young children encountering the virus for the first time, but adults can develop it too. The virus spreads through direct contact, like kissing or sharing utensils.
Once you’ve been infected with herpes simplex, the virus stays dormant in nerve tissue and can reactivate during periods of stress, illness, or immune suppression. Reactivations typically cause cold sores on or near the lips, but they can occasionally affect the gums as well.
Gum Disease and Abscesses
A periodontal abscess is a pocket of infection that starts in the gums when bacteria from the mouth invade the space between the teeth and gum tissue. This forms a swollen, painful bump that can look like a sore and may drain pus. Gum disease is the number one risk factor. When plaque and tartar aren’t routinely removed, the gums become inflamed, creating pockets where bacteria thrive.
Other factors that raise the risk of gum abscesses include chronic teeth grinding and clenching, teeth damaged by injury, broken dental fillings or crowns, and a high-sugar diet. Unlike canker sores, abscesses don’t resolve on their own and need professional treatment to clear the infection and prevent it from spreading to the bone.
Autoimmune Conditions
Oral lichen planus is a chronic inflammatory condition in which the immune system attacks the mucous membranes inside the mouth for reasons that aren’t fully understood. It can appear on the gums in two main forms. The reticular type shows up as white, lacy patches that may not cause any pain. The erosive type is more troublesome: it causes red, swollen tissue or open sores that burn, along with gum inflammation.
Other autoimmune and systemic conditions can also produce gum sores. Inflammatory bowel diseases like Crohn’s, celiac disease, and Behçet’s disease all have well-documented links to recurring oral ulcers. If you get frequent, stubborn gum sores alongside other symptoms like digestive issues, joint pain, or skin rashes, the sores may be a surface sign of something broader.
Nutritional Deficiencies
Low levels of specific nutrients have a direct connection to mouth sores and gum problems. Vitamin B-12 and folate deficiencies can cause anemia, which commonly presents with a sore, red tongue and mouth ulcers. Iron deficiency produces similar symptoms. These deficiencies are especially common in people with restrictive diets, absorption problems, or heavy menstrual periods.
If your gum sores keep coming back despite good oral hygiene and no obvious injuries, a blood test checking B-12, folate, iron, and zinc levels can be revealing. Correcting the deficiency often reduces or eliminates the sores entirely.
When a Sore Could Be Something Serious
Most gum sores are harmless, but oral cancer can start as a sore that simply won’t heal. The key warning signs are a lip or mouth sore that persists beyond two weeks, a white or reddish patch on the inside of the mouth, a lump or growth, loose teeth, mouth or ear pain, and difficulty swallowing. Any one of these lasting more than two weeks warrants a professional evaluation.
A doctor or dentist will typically start with a physical exam, inspecting any sores or unusual patches. If something looks abnormal, they may take a small tissue sample (biopsy) to test for cancerous or precancerous cells. Tobacco use, heavy alcohol consumption, and HPV infection all raise the risk of oral cancer significantly.
Relieving Gum Sores at Home
For common canker sores or minor injuries, a saltwater rinse is one of the simplest and most effective home remedies. A ratio of 1 teaspoon of salt and 1 teaspoon of baking soda dissolved in 4 cups of warm water creates an alkaline solution that reduces mouth acidity, keeps the area clean, and promotes healing.
Over-the-counter products can also help. Topical gels or pastes containing benzocaine numb the area and reduce pain on contact. Antiseptic rinses containing hydrogen peroxide help keep the sore clean and may speed recovery. For best results, apply these products as soon as a sore appears rather than waiting for it to worsen. Avoiding spicy, acidic, or rough-textured foods while a sore is active will also cut down on irritation and pain.
Sores that are unusually large, spreading, extremely painful, accompanied by fever, or recurring frequently may need prescription treatment. A pattern of more than three or four outbreaks per year, or sores that routinely take longer than two weeks to heal, is worth investigating further.