Question:
There's a discussion going on on the vegetarian bulletin board about canker
sores, but no one seems to be sure what causes them. The consensus (based
mainly on "my doctor said. . .") is that they are caused by a herpes virus,
but there seems to be confusion between the lip sores associated with oral
herpes, and canker sores inside the mouth. Does anyone out there know what
causes canker sores (a virus, bacterium, or multiple causes?)
Answer:
The cause of canker sores (aphthous stomatitis) is not known. It does not seem to be
due to herpes viruses, unlike cold sores which are generally caused
by herpes simplex virus type I.
There is some evidence that there may be a role for a streptococcal
bacteria in causing the sores, and so some people try to prevent
recurrences with antibiotic mouth rinses. Presumably the bacteria
could trigger an autoimmune response that produces the sores.
Topical steroid preparations seem to be helpful if started early
after a canker sore begins to develop.
