Sometimes the dog will eat something it shouldn’t. Sometimes it’s not a poisoning, it’s annoying, like a cake, or a pile of chicken skin and you know it’s going to cause diarrhea, BAD.
Other times it’s medicine or some other toxic molecule or poisoning substance.
How and When to Induce Vomiting: Use Hydrogen Peroxide for Poisoning
In any event, TWO HOURS is an important parameter to recall, because stomach-emptying occurs within two hours, so if your dog JUST ATE that bunch of grapes 5 minutes ago, it’s fine. Induce vomiting. Good-t0-go.
But if you discover a problem closer to, or AFTER the two hour window, it’s going to be a problem.