The vet gave me a few packets of Purina Veterinary Diets Fortiflora when Paolo had gastritis as he was throwing up back in January. It took care of it quickly. Last week he was throwing up at mid night as before. I started giving him this product again (I bought it on Amazon) and the first night I gave it to him it took care of it. It will take care of any diareaha too. As long as it's not a serious illness this product works great. Paolo has a sensitive stomach.