What Causes Mouth Ulcer?

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Mouth ulcers are also known as canker sores, are generally painful, small lesions that develop at the base of your gums or in your mouth. They can make eating, drinking, swallowing, and talking uncomfortable.

Women, teens, and even people with a family history of mouth ulcers are generally at a higher risk for developing mouth ulcers.

Mouth ulcers are generally not contagious and usually go away within one to two weeks. However, if you get a large or acutely painful sore, or if it lasts for a long time without healing, you should seek advice from your doctor.

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Mouth ulcers are painful sores. Although they are uncomfortable, they are usually harmless and most clear up by themselves within a week or two. These are common and can generally be managed at home, without visiting your doctor. 

Here we discuss the important aspects of mouth ulcers and what you need to know to keep in mind when you have these sores.

What are Mouth Ulcers?

A mouth ulcer is erosion or loss of part of the delicate tissue that lines the inside of your mouth. It is primarily the mucous membrane inside your mouth. 

Many factors cause mouth ulcers. The most frequent cause is an injury, such as accidentally biting the inside of your cheek. Few other reasons include aphthous ulceration, viral, bacterial, and fungal infections, certain medications, skin rashes in the mouth, and chemicals. 

An ulcer that does not heal might be a sign of mouth cancer. Most mouth ulcers are harmless and resolve by themselves. These sores heal within 10 to 14 days without the need for any treatment. 

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What are aphthous ulcers? Aphthous ulcers are recurring ulcers that affect around 20 percent of the population. In most people, there is no known cause for aphthous ulcers. These ulcers may be due to an underlying deficiency of Vitamin B, folate, or iron in some people.

What are mouth ulcers that do not heal? Discuss with your dentist if your mouth ulcers do not clear up within two weeks or if you start getting them frequently.

It is essential not to ignore an ulcer you have had for more than a couple of weeks. Mainly if you use tobacco products and drink alcohol frequently, this is because both these conditions increase your risk of mouth cancer.

These ulcers are painful sores that generally appear inside your mouth. They are usually yellow or red. But they are different from cold sores as cold sores occur on the outer lips and are often caused by a virus.

What Does a Mouth Ulcer Look Like? 

Mouth ulcers are usually oval or round that commonly appear inside your mouth on your cheeks, lips, and tongue. They can be white, red, yellow, or grey and are usually swollen.

It is possible to have more than one mouth ulcer at a time, and the sores may spread or grow.

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Mouth ulcers should not be confused with cold sores. Cold sores are small blisters that develop on your lips or around your mouth. Cold sores often begin with itching, tingling, or burning sensation around your mouth.

What Causes Mouth Ulcer?

In many cases, the reason for mouth ulcers is unclear. Most single mouth ulcers are caused when there is damage to the inside lining of the mouth. For example:

  • accidentally biting the inside of your cheek
  • poorly fitting dentures
  • hard to bite food
  • a defective filling

It is not always clear what causes mouth ulcers that keep returning, but some triggers include:

  • Anxiety and stress. 
  • Hormonal changes. Some women develop mouth ulcers during their monthly period.
  • Eating certain foods like chocolate, coffee, spicy foods, peanuts, almonds, strawberries, cheese, tomatoes, and wheat flour could lead to ulcers.
  • If your toothpaste contains sodium lauryl sulphate.
  • Quit smoking. The first time you stop smoking, you may develop mouth ulcers.
  • Your genes might also play a role. It has been observed that around 40% of people who keep getting mouth ulcers report that the disease runs in their families.

Medical conditions

Mouth ulcers are sometimes be caused by certain medical conditions, like:

  • Vitamin B12 or iron deficiency. 
  • Viral infections like cold sore virus, chickenpox, and hand, foot, and mouth disease.
  • Crohn’s disease is a long-term medical condition that often causes inflammation of the lining of your digestive system.
  • Coeliac disease is a common digestive condition. Seen in people who have an adverse reaction to gluten.
  • Reactive arthritis is a condition that causes inflammation in different parts of your body. It is usually caused as a reaction to an infection
  • The weakened immune system, for example, due to HIV or lupus.
  • Behçet’s disease is a rare and poorly understood condition. The condition also causes swelling of the blood vessels.

Types of Mouth Ulcers

Typically ulcers appear on your inner cheeks and last for more than one week. Most of them are harmless and do not affect healthy gums. These sores clear up with no medical intervention.

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There are three main types of mouth ulcers:

1 Herpetiform ulceration (HU)

Herpetiform ulcers are a subtype of aphthous ulcers. They get the name because they closely resemble the sores associated with herpes.  

HU is not contagious, but herpes is infectious. HU ulcers recur very quickly. You might feel that the condition never gets better.

2 Minor ulcers

This type of ulcer can range in size from 2 mm to 8 mm. These ulcers typically take a couple of weeks to get better and might cause minor pain. 

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3 Major ulcers

These are bigger than minor ulcers; major ulcers are often irregular in shape. They can also be raised and penetrate deeper into your tissue than minor ulcers. On the other hand, they can take several weeks to go away and likely cause scarring when they clear.

How to Treat Mouth Ulcer

Mouth ulcers do not usually need to be treated because they tend to clear up by themselves within a few weeks. 

However, treatment can help reduce swelling and can ease any discomfort. Treatment can be helpful if you keep getting mouth ulcers or your mouth ulcers affect eating and drinking.


Here are few things you can do to speed up healing include:

  • Apply a protective paste recommended by your pharmacist.
  • Use a soft toothbrush to brush your teeth.
  • Using a toothpaste that does not have sodium lauryl sulfate, might be irritating. 
  • Avoid hard, spicy, salty, acidic, or hot food and drink until your ulcer heals.
  • Use a straw for drinking cool drinks.
  • Avoid any substance that might trigger your mouth ulcers.

Pharmacy medicines

Several types of mouth ulcer treatment are available from a pharmacy. Speak to the pharmacist that would be best for you. Options include the following:

  • You can use an antimicrobial mouthwash to speed up healing and prevent infection of your ulcer. Children below two years should not use this treatment. The mouthwash also contains chlorexidine gluconate, which might stain teeth, but this may fade once treatment is finished. 
  • You can take painkillers that are available as a mouthwash, gel, lozenge, or spray. Mouthwash can be diluted with water if stinging continues. Children below 12 should not use gel or mouthwash. More than seven days continuously you should not use mouthwash.

Is it Mouth Cancer?

Only in a few cases, a long-lasting mouth ulcer can be a sign of mouth cancer. If ulcers are caused by mouth cancer, they usually appear on or under the tongue, although they can be noticed well on other areas of the mouth.

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Risk factors for mouth cancer include:

  • Smoking or using products that contain tobacco could increase your risk.
  • Drinking alcohol, especially smokers who are also heavy drinkers, have a higher risk than others.
  • Infection with the human papilloma virus (HPV). This virus causes genital warts.

It is important to detect mouth cancer at the earliest. If mouth cancer is detected early, you will have chances of a complete recovery. The chances of a complete recovery are good. You should get regular dental check-ups done as it is the best way to detect the early signs.

Tips to Prevent Mouth Ulcer

You should take steps to reduce the occurrence of mouth ulcers. You should strictly follow foods that irritate your mouth. That includes acidic fruits like oranges, pineapple, grapefruit,  or lemon, chips, nuts, or anything spicy.

Instead, you should choose whole grains and alkalis, meaning non-alcoholic fruits and vegetables. Eat a strict healthy, well-balanced diet and try taking a multivitamin daily.

You should try to avoid talking while you are chewing your food to reduce accidental bites. Also, try reducing stress and maintain good oral hygiene by brushing after meals, and using dental floss daily may also help. 

You should also avoid chewing gumFinally, get adequate rest and sleep. These small steps will not only prevent mouth ulcers but a host of other illnesses as well.

Many people often use soft bristle toothbrushes as it might reduce irritation in your mouth. Many also avoid mouthwashes that contain sodium lauryl sulfate. Your dentist can give you wax to cover orthodontic or dental mouth devices that have sharp edges.

If your ulcers interfere with your normal daily activities, or have persisted for a couple of weeks, see your dentist or an oral medicine specialist.


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