What do i do if my dog eats a hair tie?

That depends on the size and material of the hair tie and the size of your dog. A Lab would have an easier time passing an average-sized, not-real-stretchy hair band compared to a tea-cup chihuahua that ate a large and very stretchy hair band, especially if it had hair wrapped in it. In most cases an object like a hair band would move through the GI tract okay, but there's always a chance it could get caught up in the intestine. You would want to watch for abdominal discomfort, decreased appetite, decreased activity level, vomiting, and not being able to pass stool. The best thing to do, of course, is to keep all your hair ties (and other objects) out of his reach.

I've heard of some people feeding certain foods when their dog ingests something unnatural and potentially dangerous. (Maybe high fiber food?) Read up on foods that help with digestion in case that happens. Definitely watch for all the symptoms that Shannon mentions and be ready to go to the vet.