Help! My Cat Has Rodent Ulcers! (Vet Answered)
This question has been answered by a vet
Veterinarian & Animal Behaviorist
With nearly two decades in veterinary medicine, Dr. Paola brings hands-on experience across multiple species. A graduate of the University of Guadalajara, she specializes in preventive care, animal welfare, and positive reinforcement training.
The Question
“Hi Dr. Paola,
Sonny, my 15-year-old cat, was diagnosed several years ago with rodent ulcers in his mouth. He had regular monthly injections for a long time until they didn’t seem to be helping anymore. I found a supplement that helped for the past 2-3 years but now the condition is flaring up again and he appears to be in pain. What do you suggest?”
– Mary Helen
Quick Info about Sonny
Hello Mary Helen,
Rodent ulcers, part of the eosinophilic granuloma complex, often cycle through periods of improvement and flare-ups when the underlying trigger is still present. In senior cats like Sonny, a recurrence after a stable period usually points to ongoing hypersensitivity, most commonly linked to stress, certain food proteins, environmental allergens, or fleas, even when these are not obvious at home. The fact that he now appears uncomfortable is important, as these lesions can become painful and interfere with normal eating and grooming.
Since the injections are no longer effective and the supplement has lost its benefit, this is a good time to reassess the overall approach rather than simply switching products. Corticosteroids remain the most reliable way to control active lesions, but in older cats, we use them carefully and often combine them with strategies such as strict flea control (even if Sonny is an indoor kitty), a proper elimination diet, or other medications that help regulate the immune response, since steroids are not ideal long-term. Pain relief and treatment of any secondary infection may also be needed to improve his comfort quickly.
Because rodent ulcers can have an underlying viral component, some cats can benefit from lysine supplementation, but I would recommend discussing this with your regular vet first.
Because Sonny is an older cat and showing signs of pain, an in-person veterinary exam is important to evaluate the lesions and rule out other conditions that can look similar, including oral tumors or infections. Therefore, a hands-on assessment should be prioritized to keep him comfortable and eating well.
Best wishes,
– Dr. Paola