Mouth ulcers are a common condition and usually appear suddenly, causing pain. They are like small sores that appear on the inside of your cheeks. They can also be found on the edge of the tongue, or underneath it and, sometimes on the roof of your mouth.

They usually go away within one to two weeks without treatment but can come back within three months for some people.

What causes mouth ulcers?

No one knows the exact cause but some people tend to get them more often than others, especially if there is a family history of mouth ulcers.

Mouth ulcers are most common in children and young adults. Students and those under a lot of stress may get them often. Some women can get mouth ulcers before their periods or during pregnancy. Occasionally, they can be the sign of a more serious disease.

Other possible causes of mouth ulcers:

  • Damage to the inside lining of your mouth by very hot or acidic food and drinks.
  • Biting your inner cheek.
  • Brushing your teeth and gums very hard.
  • Poorly-fitted dentures
  • A very dry mouth – due to a medical condition or from some medicines
  • Eating food to which you are allergic.
  • Scraping of the mouth lining by sucking hard sweets.
  • Lacking certain vitamins and minerals in your body such as folic acid, and the B-group vitamins or iron.
  • Certain medicines
  • Stress and emotional factors at work or home may cause a recurrence or delay in healing but do not seem to be a cause.
Signs and Symptoms
  • Mouth ulcers are round or oval shaped, and usually less than 1cm in size. They are yellow to grey in colour on the inside, with a swollen red edge.
  • They can be very painful, especially when eating or drinking.
  • Some people can get a tingling or burning feeling 1-2 days before the ulcer appears.
  • Small blisters or sores on the outside of your lips are usually cold sores if unsure of the blister check with the pharmacist.
Mouth ulcers can heal within 7-14 days without treatment (and leave no scars), but medicine can provide relief during the time until the ulcer is healed. Medicines can numb the pain, protect the ulcer from further damage, or decrease any possible bacterial infection. Some medicines may speed up healing if used early enough.

Local anaesthetics:

e.g. Lignocaine, benzocaine help to numb the pain.

Topical analgesic:

e.g. Choline salicylate produces low levels of salicylate and can therefore be used in children.


e.g. Chlorhexidine gluconate and cetylpyridinium chloride help to prevent bacterial infections, which can increase discomfort and delay healing. Products containing chlorhexidine gluconate may discolour the tongue and teeth.


  • One of the most popular treatments.
  • Form a protective layer over the mouth ulcer.
  • Some also contain medicines that numb the pain.
  • Are difficult to maintain in contact with the ulcer, and so need to be applied often.

Mouth Washes

  • Are useful for inaccessible ulcers or clusters of ulcers.
  • Can help to prevent bacterial infection.
  • Some can numb the pain
  • Work best if you start to use them as soon as you feel the tingling sensation.

Liquid Paints

  • Form a protective layer over the ulcer but need to be re-applied often.
Visit your doctor or pharmacist:
  • If mouth ulcer is larger than 1cm or there are lots of tiny ulcers that join together to form a large ulcer.
  • If the ulcer is there for longer than 2 weeks.
  • If the ulcer bleeds.
  • If the ulcer occurs often, e.g. every 1-2 weeks.
  • If a sore throat is present or a rash on the face or any part of the body.
  • If the patient has diarrhoea as well.
  • If the patient is pregnant or breastfeeding.
  • Children with a mouth ulcer.
Helpful Tips from Mulligans Pharmacy:
  • Take a pain reliever e.g. paracetamol, if pain is severe.
  • Suck on an ice cube to help reduce the pain of the mouth ulcer.
  • Avoid spicy or acidic food and drinks when you have a mouth ulcer.
  • Avoid very hot food and drinks.
  • Brush your teeth with a soft toothbrush straight after eating. If you can't brush your teeth, rinse your mouth with warm water or use Chlorhexidine mouthwash.
  • If dentures cause your mouth ulcers, have their fitting re-checked.
  • Take vitamin B and C supplements if you are run-down especially for women and students who get mouth ulcers often.
  • Drink lots of water to avoid dry mouth.
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