Cold Sores and Aphthous Ulcers


A Sore in the mouth makes it painful to eat and talk. Many healthy people suffer from recurrent mouth sores.

The most common recurrent oral lesions are fever blisters (also called cold sores) and canker sores (aphthous ulcers). When they occur in the mouth, it may be difficult to distinguish one from the other. Since the treatment and cause of these two sores are completely different, it is extremely important to know which is which.

What Are Fever Blisters (Cold Sores)?

Fever Blisters are fluid filled blisters that commonly occur on the lips. They occur in the mouth particularly on the gums and roof of the mouth (hard palate), but this is rare. They are usually painful. The pain may precede the appearance of the lesion by a few days. The blisters rupture within hours, then crust over and last for about 7-10 days.


  • They result from a herpes simplex virus that becomes active.
  • This virus is latent (dormant) in afflicted people.
  • It can be activated by conditions such as stress, fever, trauma, hormonal changes, and exposure to sunlight.
  • When lesions reappear, they tend to form in the same location.

Can Fever Blisters Be Spread?

Yes, the time from blister rupture until the sore is completely healed is the time of greatest risk for spread of infection. The virus can spread to our own eyes and genitalia, as well as to other people.

Tips for Preventing Sores:

  • Avoid mucous membrane contact when a lesion is present.
  • Do not squeeze, pinch or pick at the blister.
  • Wash hands carefully before touching your eyes or genital area, or another person
  • Despite all caution, it is important to remember that it is possible to transmit herpes virus even when no blisters are present.


It consists of coating the lesions with a protective barrier ointment containing an antiviral agent. A 5% acyclovir ointment, there is no cure, but there is much research activity underway in this field. Contact your doctor or dentist for any information.

What are Canker Sores?

These sores are small, shallow ulcers occurring on the tongue, soft palate, or inside the lips and cheeks. It is also called as aphthous sores. They are quite painful and usually last 5-10 days.

The best available evidence suggests that they result from an altered local immune response associated with stress, trauma, or local irritants, such as eating acidic foods (i.e., tomatoes, citrus fruits and some nuts.)

Can Canker Sores Be Spread?
No, since they are not caused by bacteria or viral agents, they cannot be spread locally or to anyone else.

The treatment is directed towards relieving discomfort and guarding against infection. A topical corticosteroid preparation such as triamcinolone dental paste or Betnesol tablets dissolved in water (Kenalog in Orabase 0.1%) is helpful. Unfortunately, no cure exists at present.

What About Other Sores?

For any mouth lesion that does not heal in two weeks, you should see your physician or dentist.