While many probiotic products haven’t been put to a rigorous scientific test, there is evidence that in huge amounts, some kinds of “friendly” bacteria can be helpful.

Small studies have suggested that certain probiotics might help treat or prevent some types of gastroenteritis, diarrhea and allergic skin reactions, and the bugs are being investigated for many other ailments.

The NIH has declared the study of gastrointestinal bacteria and probiotics a major research initiative. The agency’s upcoming meeting will highlight current science so it can identify research gaps and determine the direction of future research, said Crystal McDade-Ngutter, who heads an NIH working group on the topic.

“The fact that there are a number of health implications and a lack of understanding associated with the use of pre- and probiotics makes this a very interesting subject to study,” she said.