CanIGiveMyDog.com states that while popcorn is not toxic for dogs, it is not recommended. A dog should only be given completely plain popcorn devoid of any salt, sugar or oil. Popcorn also can be a choking hazard, especially for small dogs.
CanIGiveMyDog.com states that plain popcorn could serve as a digestive aid and an energy enhancer for dogs, due to its fiber and carbohydrate properties. CanIGiveMyDog.com warns of the possibility of a dog swallowing the popcorn without completely chewing it and potentially choking on the unchewed kernels. An unchewed popcorn kernel can also cause a dog to experience stomach irritation.