It's very complicated to say, for probiotics for crohn you would likely want an anti-inflammatory probiotic, and they exist, that's not the issue. The issue is that many of those probiotics need the NOD2 signaling to activate, and since many crohn people have defective NOD2 signaling, the probiotics will never get a chemical signal to do their job. If it was cheap to tell who has a defective NOD2 and who doesn't it would be a lot easier to say which probiotics might work. Someone with a correctly working NOD2 might say "probiotics X is great", but give probiotic X to another person with a defective NOD2, also suffering from crohn, and it might do didly squat. Research is looking for probiotics that are both anti-inflammatory and that do not depend on the NOD2 protein to do their job.
You could say, why not get a bunch of probiotics, like those probiotic drinks. Since probiotics are bacteria, they need something to survive, most of them survive on sugar, that's why all the drinks are full of sugar. But when you glug down the drink you are not just getting probiotics, you are getting a whole lot of sugar also, and bad bacteria love sugar, any undigested sugar is used by them to survive in your gut, you are feeding the exact buggers you were trying to kill in the first place. There are more expensive probiotics that do not need sugar to survive, they also don't require freezing, but they're easily $30 or more, and you need the right strain. There's also some capsules out there that are quite useless, unlike UC, we as crohn patients need those probiotics to survive all the way down, and if the capsule or drink opens too soon, it won't arrive where it's supposed to go. Some capsules have a special coating that makes them last longer, but not all.
I still think probiotics work, but just taking whatever probiotic likely does more harm than good, the gut ecosystem is very fragile.
