The vet gave me some of this for Scooter week before last when he had the pukes. I used it 3 days, alternating ears (per package instructions), starting with the left ear. It worked very well for his appy, but on the 4th day his left ear (the ear that got 2 doses) was kind of scabby and raw. I guess he had some kind of reaction to it. It didn't seem to bother him and it healed up quickly with a little Halo salve.