IBS help?

My husband has chronic IBS, he was diagnosed with it a few years ago but he’s had it for 20+ years. So basically he has diarrhea everyday, multiple times a day. He doesn’t really know what causes it only that it can be triggered by pretty much anything he eats or drinks. Does anyone have any suggestions or knowledge of what he can do to cure it ? Thank you

(He doesn’t drink soda, he stopped drinking coffee, no changes)