Mouth sores

Mouth sores can be caused by infection, injury or oral cancer. Understanding the cause of the sore or ulceration will help inform how it can be treated.

Prevention and treatment advice for common mouth sore conditions

Mouth infections and ulcerations

Primary herpetic gingivostomatitis

Primary herpetic gingivostomatitis is a highly contagious viral infection.

It causes fever, irritability, headache, pain on swallowing and swelling of the lymph glands. Within a few days, the mouth and gums become painful and very inflamed. The lips, tongue, inside the cheeks, palate, and throat may become sore. Yellow fluid-filled sores then develop, burst and form shallow, ragged and extremely painful ulcers covered by a greyish skin.

Consult your dental or medical practitioner for advice and treatment.

Cold sores

Cold sores, or herpes simplex, usually occur on the lips and tongue, although they can also occur on the eyes, nose and hands. Take care not to infect another person while the sores are open and weeping.

Cold sore ointments available over the counter from pharmacies may relieve some discomfort.


Thrush, or candidiasis, is a fungal infection that initially presents as red areas of tissue in the mouth. As thrush progresses, a white flaky layer may appear on the tongue, gums or inside the cheeks. Although the white flaky layer can be easily wiped away, the tissues underneath often look ‘raw’. To avoid transmitting the infection, practice good hygiene by washing your hands and not sharing utensils.

Consult your dental or medical practitioner for advice and treatment.

Hand foot and mouth disease

Hand foot and mouth disease is highly contagious, but not serious. It is relatively common in children, and is unrelated to the animal diseases with similar names.

Symptoms include blisters inside the cheeks, gums and on the side of the tongue, as well as hands and feet. Children with hand foot and mouth disease may have a fever, be listless and may not eat well for a day or two. The blisters usually persist for 7 to 10 days, and are contagious while they contain fluid.

Consult your dental or medical practitioner for advice and treatment.

The best form of protection is good hygiene:

  • wash hands with soap and water for at least 15 seconds and dry thoroughly before handling food, after going to the toilet and changing nappies
  • implement good cleaning procedures
  • allow blisters to dry naturally and do not deliberately pierce blisters as the fluid is infectious.

Angular cheilitis

Angular cheilitis can be caused by fungal and/or bacterial infection, poor nutrition or immune deficiencies.

Angular cheilitis appears as cracked, red crusting at the corners of the mouth, which often bleeds when the mouth is opened.

To prevent the infection, keep lips moist with lip balm, practice good oral hygiene and keep hydrated by drinking lots of water. Consult your dental or medical practitioner for advice and treatment.

Dental related


Dental abscesses are pus-filled swellings caused by infection inside a tooth, infection of the gum and/or injury to the tooth. Abscesses are often painful, but not always.

Dental abscesses can cause facial swelling and/or enlarged lymph glands. In rare cases, dental abscesses can cause more widespread infection and may be life threatening.

To treat dental abscesses:

  • control moderate pain using over the counter pain medication
  • use cold compresses to help control swelling
  • take antibiotics if prescribed to reduce infection
  • seek prompt dental treatment—an abscess will not heal itself, and antibiotics will only reduce the infection in the short term.

Trench mouth

Trench mouth, or acute necrotising ulcerative gingivitis, is extremely painful. It appears as yellow-white ulcers that bleed easily.

The infection is caused by poor oral hygiene, but stress and smoking often contribute. Patients often report a metallic taste in their mouth and the sensation of their teeth being wedged apart. In some cases, patients also have swollen lymph glands, fever and fatigue.

Consult your dental or medical professional for advice and treatment.

Mouth injuries

Mouth injuries can cause bleeding, ulcers and sore spots. If you injure your mouth:

  • Apply a clean bandage or folded handkerchief to the wound and apply firm pressure.
  • Sit down and maintain the pressure for at least 10 minutes. Don’t lie down flat.
  • If you cannot control the bleeding, seek immediate medical attention.
  • Apply a cold compress to relieve swelling and pain.
  • Seek dental or medical advice so your teeth and mouth can be checked for serious injury.

The mouth cannot be sterilised so there is always a risk of infection to a mouth wound. Warm saltwater used as a mouth rinse may aid healing.

Bitten lip or cheek

A bitten lip or cheek can occur during eating or as a result of a fall. More serious bites are sometimes seen after a patient has a local anaesthetic. If the patient sucks, bites or rubs the numb area, they can damage the tissue without realising it. The traumatised area often looks like a chemical burn.

When feeling returns, this injury may be very sore and look unsightly. Swelling and infection may also occur. Warm salt water used as a mouth rinse may aid healing. If an infection occurs, consult your dental or medical practitioner.

Traumatic ulcers and sore spots

Ulcers and sore spots can be caused by damage to skin and can occur anywhere in the mouth. Dentures, braces, plates, toothbrushes, chemicals, allergies, poor nutrition, infection and hormones can all cause ulcers. Ulcers can be very painful.

Warm saltwater used as mouth rinse may aid healing and provide relief. Over the counter products from the pharmacy may provide temporary relief. If ulcers are persistent, consult a dental practitioner for advice and treatment.

Oral cancer

The majority of ulcers and swelling in the mouth and neck are not cancer, and early examination and treatment will heal most conditions. In the early stages, most oral cancers are not painful. The first symptom is usually discomfort produced by the mass of tumour tissue. If you experience any of the following warning signs, seek urgent medical advice:

  • any sore or ulcer on the tongue, cheek or gums that does not heal within 2 weeks
  • red or white patches in the mouth or on the lips
  • a swelling or lump anywhere in the mouth or neck
  • difficulty swallowing and speaking
  • repeated bleeding in the mouth, and/or
  • numbness or loss of feeling in any area of the mouth.

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