@205381b6 sounds like you're on the right path already! Mast cell activation syndrome is specifically mentioned in my GAPS book as well. The reasoning is that the gut lining is damaged and lets in too many undigested particles into the blood stream, causing allergies and other problems like MCAS. 

I'm doing the GAPS introduction diet soon, which is specifically to heal the gut lining. That diet consists out of mostly meat broths to start with. I wish I had my own chickens too! 

 @aba3e4c9 are those suitcases dripping? 

 @205381b6 maybe the GAPS method (https://gaps.me) can help you out. It's a broad method you can tailor to your own situation and has been successful with all sorts of chronic problems, like food allergies. You go back to the bare essentials to heal your gut lining, then introduce more and more food (fermented foods are an important part of it). 

Can you still eat fish, chicken and eggs? And were you able to eat red meat before?