There are millions of strains of bacteria in the world and most people when they think about bacteria they associate it with being bad or infectious. However there are strains of bacteria that are "good" and they are called probiotics. Probiotics are live microorganisms that are primarily known for their benefits towards gut health and regulation. Even though there is more research to be done on "good" bacteria, there has been evidence that probiotics offer substantial health benefits.
There are two ways in which probiotics work in the body. The first way is its influence within the digestive tract. We now know that our digestive tract needs a healthy balance between the good and bad bacteria in order to maintain a happy medium. Our lifestyle choices is what could cause this balance to fluctuate for the better or for the worst. There could be a combination of things that promote bad bacteria in the gut including stress, lack of sleep, antibiotic overuse, and so on. However, when the digestive tract is healthy, it filters out and eliminates things that can damage it, such as harmful bacteria, toxins, chemicals, and other waste products. The healthy balance of bacteria assists with the regulation of gastrointestinal motility and maintenance of gut barrier function. This is why probiotics are known to help with irritable bowel syndrome, diarrhea, and other digestive conditions.
The second way probiotics work within the body is in the immune system. When the bacteria ratio is on point within the digestive system, it then allows the immune system to operate at its optimal level. The immune system is our main defense against germs and when it is not performing it's best it leaves us vulnerable to illness. That is why with the use of probiotics our body is less susceptible to allergies, colds, autoimmune diseases, acne/eczema and other infections.
More research on this subject is being performed and the benefits of probiotics has been branching out, and new areas are emerging. Preliminary research has linked them to supporting the health of the reproductive tract, oral cavity, lungs, skin and gut-brain axis, and the prevention and treatment of obesity and type 1 and type 2 diabetes.