Most every comprehensive probiotic formula will include FOS because it increases the effectiveness of the probiotic.
Purpose of FOS
FOS serves as a prebiotic; that is, the probiotics actually feed on it and help them to produce more healthy bacteria inside the body.
What it FOS
FOS stands for Fructooligosaccharide; It is another name for it is inulin. FOS is not a probiotic or bacteria, however, if provides the material that bacteria uses to grow
Where Does FOS Come From?
FOS is naturally occurring fiber from chicory root (not a chemical). In fact the body even produces it on its own.
Will FOS increase the pathogenic bacteria in my dog’s body?
If the amount is small, and there is a good supply supply of friendly flora in the formula (at least 2 Billion), FOS would not lend to increasing any harmful or pathogenic bacteria in your dog’s body.
There are no known contraindications, other than possibly producing gas if the dose is too high. If your dog experiences gas after beginning probiotic supplementation, it is usually temporary. Read: Why Did Probiotics Increase My Dog’s Gas?