A couple of months ago, my husband and I had to take Soni in to get his final boosters before he got neutered. Well, several days prior to the appointment we began to notice red sores in Sonis mouth. When husband took him to the vet he made sure to point it out. I called, later, to check up on Soni and chatted with the tech for a while about him. It turned out that they were not able to give his boosters because Soni had rodent ulcers on his mouth. He was given a couple of injections and sent home (He returned a week later for his boosters and then a week or so after that to get neutered). I think he is getting them again as I noticed a similar bump on his upper lip. Are there any preventatives or remedies that are effective in keeping them away or getting rid of them? Maybe it is the food? What causes them?