Different types of sores can appear anywhere in the mouth, including the inner cheeks, gums, tongue, lips, or palate.
Most mouth sores are cold sores (also called fever blisters), canker sores, or other irritation caused by:
- A sharp or broken tooth or poorly fitting dentures
- Biting your cheek, tongue, or lip
- Burning your mouth from hot food or drinks
- Chewing tobacco
Cold sores are caused by the herpes simplex virus and are very contagious. Usually, you will have tenderness, tingling, or burning before the actual sore appears. Cold sores usually begin as blisters and then crust over.
The herpes virus can live in your body for years. It only appears as a mouth sore when something triggers it, such as:
- Another illness, especially if there is a fever
- Hormone changes (such as menstruation)
- Sun exposure
Canker sores are NOT contagious. They can appear as a single pale or yellow ulcer with a red outer ring, or as a cluster of these sores. The cause of canker sores is not clear, but may be related to:
- A virus
- A temporary weakness in your immune system (for example, from the cold or flu)
- Hormone changes
- Low levels of vitamin B12 or folate
For unknown reasons, women seem to get canker sores more often than men. This may be related to hormone changes.
Less commonly, mouth sores can be a sign of an illness, tumor, or reaction to a medication. Such illnesses can be grouped into several broad categories:
Drugs that may cause mouth sores include:
- Barbiturates (used for insomnia)
- Chemotherapy drugs for cancer
- Gold (used for rheumatoid arthritis)
- Phenytoin (used for seizures)
Mouth sores usually go away in 10 to 14 days, even if you don't do anything. They sometimes last up to 6 weeks. The following steps can make you feel better:
- Avoid hot beverages and foods, spicy and salty foods, and citrus.
- Gargle with cool water or eat popsicles. This is helpful if you have a mouth burn.
- Take pain relievers like acetaminophen.
For canker sores:
- Rinse with salt water.
- Apply a thin paste of baking soda and water.
- Mix 1 part hydrogen peroxide with 1 part water and apply this mixture to the sores using a cotton swab.
- For more severe cases, treatments include fluocinonide gel (Lidex), anti-inflammatory amlexanox paste (Aphthasol), or chlorhexidine gluconate (Peridex) mouthwash.
Nonprescription medications, such as Orabase, can protect a sore inside the lip and on the gums. Blistex or Campho-Phenique may provide some relief of canker sores and fever blisters, especially if applied when the sore first appears.
To help cold sores or fever blisters, you can also apply ice to the sore.
Your doctor may recommend antiviral medications for herpes sores of the mouth. Some experts believe they make the blisters go away sooner, while others claim that these drugs make no difference.
When to Contact a Medical Professional
Call your doctor if:
- The sore begins soon after you start a new medication
- You have large white patches on the roof of your mouth or your tongue (this may be thrush or another type of infection)
- Your mouth sore lasts longer than 2 weeks
- You have a weakened immune system (for example, from HIV or cancer)
- You have other symptoms like fever, skin rash, drooling, or difficulty swallowing
What to Expect at Your Office Visit
Your doctor will perform a physical examination, focusing on your mouth and tongue. Medical history questions may include the following:
- Are the sores on your lips, gums, tongue, lining of your cheeks, or elsewhere?
- Are the sores open ulcers?
- Are there large, white patches on the roof of the mouth or on your tongue?
- How long have you had the mouth sores? More than 2 weeks?
- Have you ever had sores of this type before?
- What medications do you take?
- Do you have other symptoms like fever, sore throat, or breath odor?
Treatment may depend on the cause of the mouth sore.
- A topical anesthetic (applied to the skin) such as lidocaine or xylocaine may be used to relieve pain (but should be avoided in children).
- An antifungal medication may be prescribed for oral thrush (a yeast infection).
- An antiviral medication may be prescribed for herpes sores (although some experts don't believe medication will make the sores go away sooner)
- Anti-inflammatory medications may be prescribed for severe or persistent canker sores.
You can reduce your chance of getting common mouth sores by:
- Avoiding very hot foods or beverages
- Reducing stress and practicing relaxation techniques like yoga or meditation
You can avoid irritation by:
- Chewing slowly
- Using a soft-bristle toothbrush
- Visiting your dentist right away if you have a sharp or broken tooth or misfitting dentures
If you seem to get canker sores often, talk to your doctor about taking folate and vitamin B12 to prevent outbreaks.
To prevent the spread of herpes sores, do not kiss or have oral sex with someone who has a cold sore or fever blister. Do not participate in these activities when you have an active cold sore. Do not share razors, lip balm, toothbrushes, or lipsticks.
To prevent cancerous mouth sores:
- Do not smoke or use tobacco.
- Limit alcohol to two drinks per day.
- Wear a wide-brimmed hat to shade your lips. Wear a lip balm with SPF 15 at all times.
Daniels TE. Diseases of the mouth and salivary glands. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 451.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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