My yorkie Deuce has been doing this reverse sneeze thing since he was young and the vet said he would eventually grow out of it. I dont know if it is coincedence but we just adopted a stray chihuahua (which they told me was medically treated for any illness) and it seems like Deuce's hacking is getting worse. It was so bad yesterday that I thought he was choking. (I had just given him a treat when it happened)
Also the chihuahua has this gray mucus in the corner of her eye every morning and now Deuce has that too. Anyone ever had these sort of problems???