We have two elderly cats who we adopted about a year ago. One had chronic stomach upsets and the other very bad skin/ ear allergies (the cats are not related to each other!)
Anyway, I fed the guy with the stomach problems prescription sensitivy food which helped (but didn't completely solve the problem) but the other cat refused to eat it and so I fed him whatever he would eat meaning nightmare supervised feeds until a friend suggested Yarrah. It is fab and has completely solved the tummy troubles. It has also meant that the allergies of the other cat are much less pronounced!
I don't know what is in normal cat food that upset them but cutting it out has helped two completely unrelated illnesses! Best of all, the cats love it and can at last be fed together!!! Am so glad I found it!