Hissy, I do not believe you are correct in mentioning that a flea biting a grooming cat causes the ulcer. My cat hasn't had a flea since I caught him wandering around as a stray when he was about 3-4 weeks old. He has been an indoor cat since then. In any case, fleas are not really a direct cause of this. The ulcers are congenital manifestations which shows it to be allergy related (which you did mention of course!) and affect the autoimmune functions. Anyway, they nearly always re-appear in the exact same spot as they were before.
I think there could possibly be a food allergen causing the problem in my case, but my dilemma is I have 3 cats- one who has to have FUS specific diet, one who is 18 years old (and battling a nasty e-coli at the moment) and the young guy. So my ability to handle 3 different diets and being a single person is difficult at best. So the little guy with rodent ulcer gets to snack on the other's foods while getting his own in a secret place the other 2 don't know about. :-) I am not completely convinced it is allergy related though- and from my research and speaking with my vet, I think the jury is still out.
Cyn: Places to keep an eye on: paws, the groin area, under the neck, and inside the mouth as well- look at the roof and under the tongue. There is also possibility that the kitty can develop them in the lungs, which of course would not be fun to diagnose and treat. FYI- my Simba's lesion appears on the upper left side of his mouth, just like in your photo, 90% of the time. In my case, so far, it's not as bad as it seems, but it just means I have to be vigilant in keeping on top of it.
Another Google search shows lots of discussions on the usenet groups,
rec.pets.cats.health+behav, alt.med.veterinary and others:http://groups.google.com/groups?q=EO...NULOMA+COMPLEX
But when reading those, as well as this discussion should always be secondary (or tertiary!) to the advice of a good caring vet, which you have already done!
Good luck with your baby! :-)