Read the book "breaking the vicious cycle" , it talks about
how an out of balance of bacteria in the gut may cause crohns. The book also goes into detail on how you can control this and put your crohns in remission with a change of diet called the SCD.
I went on the SCD diet 8 years ago when I was diagnosed with crohns in the colon and I have not had one symptom from my crohns since. I also healed to massive rectal fistulas. The only drug I have taken and still take is pentassa.