According to PetMD.com, cranberries are safe to give to your dog and might provide some small benefit in preventing urinary tract infections. However, the author of the article, Dr. Jennifer Coates, warns that it is best to use proven methods and to use cranberries only as supplements to these treatments.
Cranberries do not harm dogs, provided that the berries do not have any potentially harmful additives in them. Some studies suggest that the same benefits that humans receive from cranberries are possible for dogs. The underlying causes of the infections that cranberries help to prevent are similar in dogs and humans.