My doggy has diarrhea!!

Question
I have a 7 pound chihuhua has had diarrhea for 3 days, I am so worried that I went out last night and bought some babe electrolyte water and a chewable pepto bismol. I gave him a small quantity.. Will it hurt him???? His stool is not bloody just really runny, kind of mucousy.

Answer
No it won't hurt him but what started this is the question and how old is this dog? Is he vaccinated? He could have parvo if he is a young dog.
I always recommend taking them to the vets in a case like this. You could lose him if he has parvo and isn't treated.