All of our Pugs are tested for PDE to minimize the chances of it developing as much as possible. However, not carrying the marker does not mean 100% protection. Many factors can come into play. Any toy breed can develop it. I highly recommend minimizing the amount of chemicals or pesticides dogs are exposed to through application of topical flea meds, yearly vaccinations or year round heartworm preventative. I use those on an "as needed" basis. I am also very careful of the chemicals a dog may be exposed to in the treatment and care of lawns or fields.  Each one of the things mentioned can compromise or damage the immune system causing under or over reaction. I am also a huge proponent of giving my dogs fresh or cooked fruits and vegetables. They also eat brown rice, quinoa, oats and several other grains. Raw meat and cooked. A variety of foods!!! My dogs have never had issues with a special diet or allergies.