Shoes are not food and are dangerous for dogs to eat. Ingesting shoe material can lead to physical obstruction in the digestive tract, gastrointestinal upset, or choking. If your dog has eaten a significant piece of a shoe, seek immediate veterinary attention.
How It Affects dogs
Physical obstruction, gastrointestinal irritation, potential for chemical exposure from dyes/glues
Disclaimer: This information is for educational purposes only. Always consult your veterinarian before making changes to your pet's diet.