Cortisone injections only last a few months.

We give our cats salmon oil (CVS Brand 100% wild salmon oil capsules; we pierce them with a knife and squirt them over their wet food). We give one cat 2 1/2 capsules worth daily, and our slightly smaller cat, 1 1/2 capsules worth daily. They are also on Rx LID food because both over-groom. The larger cat also has Eosoniphilic Granuloma Complex. Symptoms, and over-grooming waxes and wanes, but the combo of the food and the salmon oil seems to keep it in check to varying degrees.