Specifically, is bacon harmful to chihuahuas?
It depends on how much they have and if the particular dog is prone to pancreatic inflammation which you can read about here http://www.peteducation.com/article.cfm?cls=2&cat=1580&articleid=335 Its not the pork its the fat that would be bad. Little dogs need tiny treats not big ones. While a small amount of the salt and preservatives and fat might not be harmful to your dog a big amount could be. Hope this helps you!