From: sbharris@ix.netcom.com (Steven B. Harris )
Subject: Re: Canker sore - the shape of the ulcer
Date: 09 Oct 1995
Newsgroups: sci.med,sci.med.dentistry

In <DG73vJ.H13@world.std.com> ae@world.std.com (Arthur Edwards) writes:

>I suffer from aphthous stomatitis, canker sores. I find the shape
>of the ulcer to be puzzling. I mean why is there a characteristic
>yellowish center and raised border in the halo shape. What I mean
>to say is why not simply an oval mass rather like a pimple. What is
>it about this type of infection or this type of tissue that results
>in the characteristic shape?

  If you have somewhat painful lesions, and always get them on the same
side, in about the same spot(s), you probably actually have a herpes
simplex infection (i.e., a "cold sore"), only one showing on a mucosal
spot (such as inside your cheek), instead of your lip.  The central
yellow is tissue being actively destroyed by virus coming out of a
nerve ending, and the red ring with edema is normal inflammatory
response of surrounding tissues reacting to the chemicals being
released from the tissue under attack.

                                        Steve Harris, M.D.