Not op but my wife has MCAS. The things that have helped the most are: Oral Cromolyn (helped sooo much with gi issues), and more recently she's started Ketotifen which is a systemic mast cell stabilizer that's seemed promising but is fairly new. She also tried Montelukast which was well tolerated but didn't make a ton of difference for her personally (but I know it helps a lot of people). Supplement wise DAO was the most useful for food truggers