Treating without Diet Mods

Just received a presumptive MCAS diagnosis from my allergist after a high PG2 level and history of improvement from antihistamines. He's starting me slow with increased Zyrtec, but has talked about trying a trial drug that calms mast cell activation (forget the name, Rh-something) or Cromolyn Sodium in a couple weeks if the Zyrtec doesn't do enough. However, he said he doesn't recommend any dietary changes, and that restricting my diet could make me more sensitive. Has anyone been successfully treated without a diet overhaul? I'd love to believe this cause I've already had to cut out a lot foods I'm sensitive to (RIP peanut butter), but I also don't 100% trust this allergist as he was quite dismissive initially, especially when most of my symptoms are GI. Any wisdom or personal experiences welcome!