Probiotics have become very popular in the human health world. Similarly, they can be used to help dogs and cats that are suffering the effects of not having enough healthy bacteria in their guts. Although cats and dogs are different species, their digestive systems are quite similar. There are billions of bacteria in the gut, which is actually part of the immune system, that help keep digestive functions operating smoothly. Studies are still underway, but initial research points to the fact that probiotics might be helpful in raising immune function as well as balancing bacteria. However, be sure to talk to your veterinarian about probiotics before administering them (or any other medicine) to your pets.