Greenies are the very popular green chew that is made for cleaning the teeth. The problem is that dogs do not chew them, but swallow large chunks. They have been responsible for obstructions in the throat and in the intestines. They are not 100% digestable and can swell in the intestines and cause a blockage. The compressed vegetable treats are the 3rd leading cause of throat obstructions (bones are #1 and fishhooks #2). As of 2006, there had been 13 reported deaths due to Greenies. To view a CNN report and watch a video go to: http://www.cnn.com/2006/US/02/14/dangerous.dogtreat/
Some vets warn against feeding rawhide and pig ears because they can contain chemical residues that can be harmful to your pet's health. Larger pieces can break off and be swallowed, getting stuck in the throat or the intestines and cause a blockage.