Several probiotic preparations have promise in preventing of various conditions. However, most studies have been small and many have significant limitations, making it difficult to make conclusions regarding their effectiviness in therapy. It is also important to understand that there are significant differences in composition and in biologic activity between various commercial preparations. (Results therefore, may vary significantly between brands.) I have notice in my practice significant enthusiasm for probiotics by the lay public and this enthusiasm seems to be more significant than the current scientific evidence of their effectiveness. Large, well designed multicenter controlled clinical trials are needed to clarify the role of specific probiotics in different patient populations.

Probiotics are generally considered safe and the decision to use a probiotic rests mostly upon the degree of anticipated benefit, available alternatives, the clarity of the available data in showing a benefit, costs, and patient preference. No probiotic strategy is currently considered to represent the standard of care nor primary treatment for any specific conditions. (http://www.uptodate.com, "Probiotics for Gastrointestinal Disease," Sartor, RB, Sept 2009)

Probiotics have been shown to have some promise in prevention and treatment of Pouchitis, Ulcerative colitis and Atopic Dermatitis, however, there is still unproven efficacy in many other areas like Crohn's Disease, Infectious Diarrhea, Irriable Bowel and Lactose Intollerance.

To date, there are no studies I am aware of showing "dependance" or tollerance. Most studies are small and still lack clear data.