Thanks for the question. It is difficult for me to say what it is though without seeing it. It does not sound like an allergic reaction however but more sounds like an autoimmune condition commonly called "rodent ulcers". These inflamed lesions do come and go and can be painful. Other then medication for the times when it gets bad, little can be done to cure them.
Thank you for the reply, I have pictures of it I'm just not sure how to post pictures ( kinda new to this Internet thing ) but that makes more sense then an alergy cuz it happens so often, but one more question, if it is the ulcers could it hurt them in the long run and will they continue to have it their whole lives?
to post a photo, go to your home page...scroll down on the left hand side you will see *photos* click on that, it will take you to an album page and in the upper right you will see the tab *upload photos' if you have photos stored on your computer you can than transfer them to this page...good luck...first must have photos stored in your computer from a digital camera.
Have you tried eliminating all grains from your kitties diet? there are many 'grain free' varieties available from good pet stores, this can sometimes help also stop feeding the same source of protein, eg..if feeding chicken try beef or venison with as FEW additives such as artificial coloring or preservatives as possible...as with many dry foods.