We call probiotics “good bacteria,” but they aren’t infection-fighting superheroes; they’re just germs that often live with us harmlessly. Scientists are still puzzling out exactly what goes on inside our intestines, and what role each microbe plays. In some cases, probiotics help, but that depends on which probiotic, and what infection or health condition you’re trying to treat, and perhaps also on what microbes already call your bowels home
https://vitals.lifehacker.com/probiotics-can-potentially-hurt-you-it-turns-out-1828803797
https://vitals.lifehacker.com/this-guide-to-probiotics-tells-you-which-brands-actuall-1779854845