S. boulardii is a special probiotic that's a friendly strain of yeast. Studies have shown that S. boulardii is safe and effective for reducing diarrhea from multiple causes. As a probiotic, it is especially helpful for regrowing gut microbe populations that have become imbalanced and for promoting healthy skin. And unlike bacterial probiotics, S. boulardii isn't affected by certain prescription medications that can affect the gut microbiome, so it can also be used during treatment to help with the digestive side effects that those medications often cause. In fact, studies have shown that when S. boulardii is given along with these medications, pets are much less likely to develop diarrhea during or after the course of medication. S. boulardii is also resistant to stomach acid, so when it reaches the intestines, it's still intact and alive, while many bacterial probiotics die in the stomach and never make it to the gut. Once in the gut, S. boulardii provides food for beneficial microbes, supporting a healthy, diverse microbiome. Fructooligosaccharides (FOS) are tiny, soluble fibers. The FOS in our S boulardii + FOS is made of non-GMO beet sugar*. These particular fibers are prebiotic, meaning that they are the preferred food of beneficial microbes like the ones in your pet's gut. Making sure all the beneficial members of the gut microbiome get enough of the right food is crucial not just for healthy digestion, but also for a strong immune system, healthy skin, and even a happy mood. Studies have shown that adding FOS to a pet's diet improves gut health and that FOS in particular offers greater benefits for pets than other prebiotic fibers. *The geographical origin of the non-GMO beet sugar is as follows: Netherlands, Poland, Denmark, France, Germany, U. K.