We consider a dog to have an "upset stomach" when he is vomiting or having loose stools are diarrhea. Sometimes, you have a fairly good idea about what probably caused your dog to have one of these symptoms. For example, tonight I can home to find that my children's dogs teamed up to get a plate of leftovers off of the table while we were out. Someone had left the food out, and if one of the dog's vomits tonight or tomorrow, I am going to assume that one of their stomachs was upset by the thousand island dressing or the cheddar cheese. If something like this happens to your dog, there are a couple of things you can do to safely look after your dog at home.
First, make a note of the time and day, so that if your home care needs veterinary follow-up you will remember exactly when the problem started. Make another note about what was in the vomit, whether or not the dog had just eaten. That is, is Fido vomiting fluid without provocation, or is he just getting up something that didn't sit right in his stomach. If your dog is tiny and could easily become dehydrated, don't put off the vet visit at all.
But for one time episodes of vomiting after getting into the trash, you are pretty safe doing the following for your dog: Boil some rice and chicken. Put it in the refrigerator so that you can feed it to him in about 12 hours. In the meantime, don't feed him anything. Let him have his water, but pick up his food dish and keep it up until his stomach has had a nice long break from any further digestion. If he doesn't vomit for the next 8-12 hours, feed him the chicken and rice, but still none of his regular food. After feeding him like this for about 48 hours, start to give him some of his regular food.
Again, this is only for a mild stomach upset associated with a brief dietary indiscretion. If vomiting occurs more than once or twice, you definitely want to take Fido to the vet as soon as possible.
Loose stools can often be cared for in the same way, and again, only if you have a very good reason to think there was something inappropriate eaten, or if you've made a sudden change in diet (not a good idea!). You may treat conservatively at home with bland food for a day, then follow up with veterinary care if there's not complete resolution.
Do you give any medications while you're waiting to see improvement with the bland food? No, no and no. Naturally bland food, a short trial of "tincture of time" and then a trip to the vet if needed.