The reason why Greenies block digestive tracts isn't clear, but it may be because the vegetable material is sticky, conforms to tubular organs or expands when it binds to liquids.
"Certainly a lot of dogs have been given Greenies that haven't had a problem but the concern is, when you have a few dogs that have had a problem, it's hard to feel comfortable that it's safe."
We found an All Natural Safe Alternative to Greenies it is called
"Terrabone." It is all natural and organic. Terrabone is the world's healthiest, the safest and smartest edible dental dog chew bone. Made in the USA! Terrabone is formulated foremost for safety, easy digestion, and pleasant handling-No Choking hazards, no green poop, and no yucky mess and odor.
Terrabone is low fat, low calorie, and high fibre with absolutely no wheat , no corn, no soy, no gluten, no artificial ingredients and no animal by-products like gelatin or animal glycerin.
If you try this product you will never go back to Greenies again. Our dogs love them and I just love giving them an all natural safer product.
Find Terrabone at http://www.ledfootspetbakery.com/ under dog chews.