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What Causes Mouth Ulcers & How To Treat Them

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 10 Aug 2022

Mouth ulcers are round or oval sores that develop inside the mouth. Although very uncomfortable, mouth ulcers are in most cases harmless. Without treatment, the majority of mouth ulcers will clear up within a fortnight, but a sufferer can experience multiple mouth ulcers at a time (which can then spread and grow).

In this article, we're looking at two things in particular: possible causes of mouth ulcers, and viable treatments.

Corsodyl Mouthwash Mint
Corsodyl Mouthwash Mint
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What causes mouth ulcers?

In some cases, the causes of mouth ulcers are still unclear. However, most single ulcers are the result of damage to the lining inside of the mouth. This damage can be the result of:

  • Accidentally biting the inside of the cheek or lips.
  • Eating hard or sharp-edged food.
  • Having dentures, braces or rough fillings that don’t fit properly.
  • Having a defective filling.

It is not always clear what causes recurrent mouth ulcers to develop, though triggers are thought to include:

  • Hormonal changes, such as during pregnancy or a period.
  • Anxiety, stress or exhaustion.
  • An iron deficiency.
  • A vitamin B12 deficiency.
  • Certain medications, including some painkillers and beta-blockers.
  • Food allergies or intolerances.
  • Certain foods, such as spicy foods, chocolate, cheese, tomatoes, strawberries, almonds, peanuts, wheat flour or coffee.
  • The initial stages of smoking cessation.

Genetics can also be a contributing factor as around 40% of recurrent mouth ulcer sufferers report that the condition runs in their family. Certain medical conditions can also cause mouth ulcers. These include:

  • Crohn’s disease.
  • Coeliac disease.
  • Hand, foot and mouth disease.
  • The cold sore virus.
  • Chickenpox.
  • Reactive arthritis.
  • Behcet’s disease.

If you find that you have multiple mouth ulcers, it could also signal that your immune system has been compromised due to a condition such as HIV or lupus. This is the case only on rare occasions, but if you’re worried, it’s best you speak to your GP.

What are the treatments for mouth ulcers?

Mouth ulcers will usually heal by themselves within one to two weeks. There are treatments available that will help reduce the swelling and ease the discomfort. Treatments that are available without prescription include:

  • Antimicrobial or antiseptic mouthwashes, such as Corsodyl, chlorhexidine gluconate, or Anbesol oral antiseptic liquid. These can help to speed up healing and prevent the ulcer from becoming infected.
  • Corticosteroid treatments, such as hydrocortisone buccal tablets, help to reduce the discomfort as well as speed up the healing process. Corticosteroid treatments are not suitable for children under 12 years.
  • Pain-killing mouthwashes, lozenges, pastilles, gels and sprays are available to help reduce the associated pain and discomfort. Examples of such treatments include Iglu Gel, Iglu Pastilles, Orajel, Bonjela Adult Gel, Difflam Oral Rinse, Bonjela Junior Gel, Difflam Spray and Dequadin Lozenges. These treatments normally include a local anaesthetic to numb the area.

If your ulcers are severe or numerous, it may be necessary to seek stronger treatment options. Your GP or dentist can issue stronger steroid treatments to help reduce the pain and swelling and speed up healing.

While your ulcers are healing, it’s important to avoid irritating them. This will ensure your ulcers heal quicker, are less painful, and are less likely to return once healed.

To avoid irritation:

  • Always use a soft-bristled toothbrush and brush your teeth gently, taking care not to brush up against your ulcers.
  • Do not use toothpaste containing sodium lauryl sulphate.
  • Drink cold drinks through straws. Try to avoid very hot or acidic drinks (fruit juices and fizzy drinks, etc.).
  • Eat softer foods and avoid rough, crunchy textures.
  • Do not eat spicy, salty or acidic foods.
  • Do not use chewing gum.
  • Visit your dentist regularly.
  • Eat a balanced, healthy diet with plenty of fruit and veg.

You should visit a GP or dentist if your ulcer:

  • Doesn’t heal within 3 weeks: this could be an early sign of mouth cancer.
  • Returns, particularly after treatment.
  • Starts to bleed or turn red and becomes more painful than usual. This could be a sign of an infection developing.
  • Grows bigger.
  • Is located at the back of your throat.

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