Mouth sores are small breaks in the tissue lining your mouth, and they have many different causes — from accidentally biting your cheek to viral infections to reactions to food or medication. Most common sores, like canker sores and cold sores, heal on their own within one to two weeks. Treatment focuses on reducing pain and helping the tissue heal, and a few simple steps at home can make eating and talking more comfortable in the meantime.
What Causes Mouth Sores And How To Ease The Pain?
The two most common types of mouth sores are canker sores and cold sores, and they have completely different causes.
Canker sores (also called aphthous ulcers) form inside the mouth — on the tongue, the inside of the lips and cheeks, and the soft palate. They are not contagious. They typically appear as round or oval sores with a white or yellow center and a red border. The exact cause is not fully understood, but research points to an immune system reaction. Triggers include minor mouth injury, stress, certain acidic or spicy foods, and toothpaste containing sodium lauryl sulfate. Some people get them more often due to nutritional deficiencies in vitamin B12, iron, or folate.
Cold sores are caused by the herpes simplex virus type 1 (HSV-1). They usually appear on or around the lips, though they can sometimes occur inside the mouth. HSV-1 is very common — the World Health Organization estimates that billions of people worldwide carry it. Once you have the virus, it stays in your body and can reactivate during times of stress, illness, sun exposure, or a weakened immune system. Cold sores are contagious, especially when the blister is visible.
Other causes of mouth sores include:
- Accidental bites or burns from hot food and drinks
- Fungal infections such as oral thrush, which is more common in people with weakened immune systems or those taking antibiotics
- Medications, including some blood pressure drugs and chemotherapy agents
- Autoimmune conditions that affect the mucous membranes
- Vitamin deficiencies, particularly B12, folate, and iron
- Food sensitivities or allergic reactions
The pain from a mouth sore comes from inflammation and exposed nerve endings in the damaged tissue. That is why acidic, salty, or spicy foods sting so much when they touch a sore.
What Is the Difference Between a Canker Sore and a Cold Sore?
People often use these terms interchangeably, but they are distinct conditions with different causes and different locations.
| Feature | Canker Sore | Cold Sore |
|---|---|---|
| Location | Inside the mouth (tongue, inner lips, cheeks) | Usually outside — on or around the lips |
| Cause | Immune reaction, injury, nutritional triggers | Herpes simplex virus type 1 (HSV-1) |
| Contagious? | No | Yes, especially when blisters are visible |
| Appearance | White or yellow center with red border | Fluid-filled blisters that crust over |
| Healing time | Usually 1–2 weeks | Usually 1–2 weeks for the initial outbreak; recurrences tend to be shorter |
Knowing which type you have matters because the treatment approaches differ. Antiviral creams and medications can help with cold sores if started early. They do nothing for canker sores, which are not viral.
How Can You Ease the Pain at Home?
Most simple mouth sores do not need medical treatment. The goal is to reduce discomfort while your body heals the tissue.
Avoid irritants. Skip acidic foods like citrus and tomatoes, spicy dishes, salty snacks, and crunchy foods that can scrape the sore. This is not a cure, but it prevents making the sore worse.
Rinse with salt water or baking soda. A mild saltwater rinse (about half a teaspoon of salt in a glass of warm water) can help clean the area and reduce inflammation. Some clinicians also suggest a baking soda rinse. These are widely recommended but have limited clinical trial evidence specifically for mouth sore healing.
Use over-the-counter topical treatments. Products containing benzocaine or lidocaine numb the area temporarily. They provide symptom relief but do not speed healing. Some gels form a protective barrier over the sore. Follow package directions carefully, and do not use benzocaine in children under 2 years old due to a rare but serious risk of a blood condition called methemoglobinemia.
Try a cold compress. Holding something cold against the outside of your lip or cheek can reduce swelling and numb the area, especially for cold sores.
Take an over-the-counter pain reliever. Ibuprofen or acetaminophen can help with pain. Use as directed on the label.
For cold sores, consider an antiviral. Over-the-counter docosanol cream and prescription antivirals like acyclovir can shorten healing time if started at the first sign of tingling or itching. Research published in the Cochrane Database of Systematic Reviews has found that oral antivirals can reduce the duration of cold sore episodes, though the benefit is modest.
Stay hydrated and eat soft foods. Yogurt, mashed potatoes, smoothies, and soft grains are easier to eat when your mouth hurts. Drink through a straw to bypass sore areas.
When Should You See a Doctor for a Mouth Sore?
Most mouth sores heal within one to two weeks without medical attention. But some situations warrant a call to your doctor or dentist.
- A sore that does not heal after two weeks
- Sores that keep coming back frequently
- Multiple sores at once, especially with fever or feeling unwell
- Sores that are unusually large or spreading
- Severe pain that makes it hard to eat or drink
- Sores accompanied by skin rash, joint pain, or eye inflammation
- A sore near the lip that crusts and bleeds repeatedly
A persistent sore that does not heal is the most important warning sign. Oral cancer can sometimes first appear as a sore or lump in the mouth that does not go away. This does not mean every lingering sore is cancer — far from it. But a non-healing sore should be evaluated by a professional.
People with weakened immune systems, those undergoing chemotherapy or radiation to the head and neck, and people with autoimmune conditions may need earlier evaluation and more aggressive management.
Can Nutrition or Lifestyle Changes Prevent Mouth Sores?
If you get canker sores often, addressing potential nutritional gaps may help. Some studies suggest that correcting deficiencies in vitamin B12, folate, iron, or zinc can reduce recurrence in people who are deficient. If your levels are normal, supplementing beyond that is unlikely to help.
Identifying and avoiding your personal triggers can make a real difference. Common triggers include:
- Toothpaste with sodium lauryl sulfate — some clinical trials have found that switching to SLS-free toothpaste reduces canker sore frequency
- Highly acidic or spicy foods
- Dental work or braces that irritate the mouth lining
- High stress periods
- Certain foods like chocolate, coffee, strawberries, eggs, nuts, and cheese — these are commonly reported triggers, though evidence is mostly anecdotal
For cold sores, managing stress, getting enough sleep, and using lip balm with sun protection can reduce reactivation. Sun exposure is a well-known trigger for cold sore outbreaks.
Good oral hygiene — gentle brushing, regular dental checkups, and keeping your mouth clean — supports overall oral health. It will not prevent every sore, but it reduces the chance of secondary infections.
What About Mouth Sores From Medication or Medical Treatment?
Some medications directly cause mouth sores as a side effect. Chemotherapy drugs are a well-known cause because they affect rapidly dividing cells, including the cells lining the mouth. This condition is called oral mucositis, and it can be severe.
Other medications linked to mouth sores include certain blood pressure medications, nonsteroidal anti-inflammatory drugs (NSAIDs), and some antibiotics. If you suspect a medication is causing sores, talk to your doctor. Do not stop taking a prescribed medication on your own.
For people undergoing cancer treatment, managing oral mucositis is a recognized part of care. Strategies may include prescription mouth rinses, oral cryotherapy (sucking on ice chips during certain chemotherapy infusions), and specific oral care protocols. This is an area where clinical guidance is well established and should come from your oncology team.
Do Home Remedies Actually Work?
Many home remedies for mouth sores have been passed down for generations. Some have modest supporting evidence, and others have none.
Honey has been studied for wound healing and has some antimicrobial properties. A few small studies suggest it may help reduce canker sore pain and size, but the evidence is limited.
Aloe vera gel has been used topically for various skin conditions. Some small trials suggest it may help with canker sore healing, but results are not consistent.
Chamomile mouthwash has been studied in small trials with mixed results. It may reduce inflammation, but the evidence is not strong enough to call it proven.
Licorice root has been investigated for canker sores in a few small studies. Results have been mixed and no large trials have confirmed benefit.
Vitamin supplements only help if you are actually deficient. Taking high doses of vitamins you do not need will not prevent or heal sores and can cause harm in some cases.
The honest position: no home remedy has strong, consistent clinical evidence showing it reliably heals mouth sores faster than the body would on its own. Some may help with pain. If a remedy is not helping after a few days, it is reasonable to stop.
Frequently Asked Questions
How long do mouth sores usually last?
Most canker sores and cold sores heal within one to two weeks without treatment. If a sore lasts longer than two weeks, see a doctor or dentist.
Are mouth sores contagious?
Canker sores are not contagious, but cold sores caused by HSV-1 are. Avoid kissing or sharing utensils, towels, or lip balm while a cold sore is visible.
Can I use benzocaine gel on a mouth sore?
Benzocaine gel can numb the pain temporarily in adults and children over 2 years old. Do not use it in children under 2 because of a rare risk of methemoglobinemia, a serious blood condition.
When should I worry about a mouth sore?
A sore that does not heal within two weeks, keeps bleeding, or comes with fever or difficulty swallowing should be evaluated by a doctor. Persistent non-healing sores can occasionally be a sign of oral cancer.
