Probiotics are popular treatments for any number of ailments (in animals and people), but marketing, especially on the veterinary side, massively outstrips research. A few years ago, I worked on probiotic development in horses. We found what looked like a good candidate bug, but instead of just trying to sell it, we did a proper trial. Despite the positive properties it showed in the lab, it actually caused diarrhea in foals compared to a placebo group. Oops. (Does that make me a bioterrorist or just a really bad probiotic developer?) Anyway, history repeated itself with another probiotic trial in foals that was just published (Schoster et al, J Vet Internal Med 2015). Despite some promising results in the lab, foals treated with this bacterial combination were more likely to develop diarrhea that required veterinary care compared to untreated foals. I don’t mean to say that all probiotics are bad. However, the “well, you have nothing to lose” approach that is often taken with probiotics (and other nutraceuticals) may not be appropriate. Probiotics, and other nutraceuticals, should be properly scrutinized like any other kind of treatment or therapy.