My experience isn't perfect with Ketotifen but it is the best MCAS med I have tried so far. I find I do better with antibistamines vs mast cell stabilizers and this being both is the best combination. It helps with fatigue and the mast cells in my stomach as well, which is unusual ihe heard, as usually cromolyn works best there but that one didn't work for me. Th side effects aren't always my favorite - namely emotional blunting - and it will flair you when you first start. but overall its a great intervention and worth trying, hopefully it works for someone else as well as it does for me.