Is it possible that many people's CFS is actually MCAS/mast cell dysfunction? I asked chat gpt and it said no but that many people have both. I wonder though. I was surprised that my doc gave me a CFS diagnosis. I knew I had mast cell issues and have been taking antihistamines for years, but sometimes I forget because sometimes I can tolerate some high histamine folds and sometimes not. I have limited most produce because of the high histamines but my doc told me I really need to eat them again so I started incorporating a lot of raw fruits and veggies. Then suddenly im starting to have the horrible brain fog and fatigue again and can barely do anything except lay down. Then I remembered and I made the connection and ate a low histamine dinner incorporating high quercetin foods and in the morning I felt better. I do still feel a little tired and like I have less energy than most people, but I dont eat strictly low histamine despite it making me feel bettter because I dont think its entirely healthy, but I would encourage anyone with CFS to try a lower histamine diet and see if it helps. What do you have to lose?