Fever Blisters and Canker Sores
If you have been bothered by a sore in your mouth that made it painful to
eat and talk, you are not alone. Many otherwise healthy people suffer from
recurrent mouth sores.
What Are Fever
Blisters (Cold Sores)?
Two of 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.
These are common names for fluid filled blisters that commonly occur on the
lips. They also can occur in the mouth, particularly on the gums and roof of the
mouth (hard palate), but this is rare. Fever blisters are usually painful; in
fact, the pain may precede the appearance of the lesion by a few days. The
blisters rupture within hours, then crust over. They last about 7-10 days.
Fever blisters result from a herpes simplex virus which becomes active. This
virus is latent (dormant) in afflicted people, but 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 your own
eyes and genitalia, as well as to other people.
- 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
Despite all caution, it is important to remember that it is possible to
transmit herpes virus even when no blisters are present.
Treatment consists of coating the lesions with a protective barrier ointment
containing an antiviral agent, for example 5% acyclovir ointment. Presently,
there is no cure, but there is much research activity underway in this field.
Contact your doctor or dentist for the latest information.What are
Canker sores (also called aphthous ulcers) are small, shallow ulcers
occurring on the tongue, soft palate, or inside the lips and cheeks. They are
quite painful, and usually last 5-10 days.
The best available evidence suggests that canker sores 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 toward relieving discomfort and guarding against
infection. A topical corticosteroid preparation such as triamcinolone dental
paste (Kenalog in Orabase 0.1%®) is helpful. Unfortunately, no cure exists at
What About Other Sores?
For any mouth lesion that does not heal in two weeks, you should see your
physician or dentist.
© 2004 AAO-HNS/AAO-HNSF
Please read our disclaimer. Any information provided on this Web site should not be considered medical advice or a substitute for a consultation with Dr. Hector N. Hernandez or other healthcare professional. If you have a medical problem, contact us for diagnosis and treatment.