Popcorn Is Not a Suitable Dog Treat
Some dog owners are tempted to toss their dogs popcorn as a dog treat. While not pure dog poison, the salt and butter in popcorn does damage to your dog's metabolism over the long term, which can lead to weight gain and organ failure. In lieu of popcorn, feed your pet dog treats instead.
Choking Hazard
Hard kernals can not only hurt the teeth, but can be a choking hazard. This is especially the case for a dog, who is likely to just swallow the popcorn without chewing.
When it comes to your dog and popcorn, the bottom line is that you likely don't have cause for concern if catch your dog nibbling at some kernels and he appears to be breathing all right after you take it away. However, you should try to keep the popcorn out of his reach in general. Make sure your dog eats a healthy diet of nutritional dog food to keep him from excessively searching for snacks elsewhere.