My GI prescribed a form of mesalamine called Lialda when I was first diagnosed. I was also told the same thing- it is the mildest of the drugs used to treat Crohn's and it wasn't likely to cause a lot of side effects. What the doctor didn't tell me is that for about 1 in 20 individuals, the medication will cause colitis. Which means that it may increase your Crohn's symptoms. Unfortunately, that is exactly what happened to me. It drastically increased diarrhea, abdominal pain, and caused bleeding (I had never had blood in the stool before). It also caused my hair to fall out in clumps. My new GI doesn't believe mesalamine is the best drug to treat Crohn's, although it can be useful in ulcerative colitis. I have heard of it helping some people with Crohn's and it is a relatively mild drug, so it is worth trying. Just be on the lookout for any increase in symptoms and make sure that you report them to your doctor. If your doctor acts like the drug couldn't possibly be causing an increase in symptoms (like my old GI did), get a new doctor. Good luck, I hope it helps you!