No question we have hypersensitivities that are both neurologic and biologic. But alcohol intolerance could be an interesting clue. So I just searched for info on alcohol metabolism, how it might relate with what is known about CFS, and got a lot of hits:
(1) Alcohol metabolism produces free radicals. So for one thing, mixing CFS with alcohol will lead to rapid antioxidant system depletion (glutathione, vitamins C, and B1/thiamine get depleted). Also, (2) alcohol is partly detoxified by the liver's P450 system (cytochrome P2E1), which is often broken in CFS. Then there is the fun fact that (3) alcohol consumption lowers ATP activity in the liver, not good for poor ATP recyclers like CFS patients. Let's see, that's three strikes. But wait, there's more, (4) one study showed that in a rat model, alcohol produces hypoxia in the liver. Given the cellular hypoxia known to be present in CFS, along with points 1-3 above, I think there are some pretty good explanations already for alcohol intolerance in CFS. Then there is the (5) simple carb issue... but if the intolerance were just about carbohydrate problems, then low-carb alcohol drinks would be better tolerated. I've not seen any data on that fifth point, but heard that 'it's the carbs' theorized by some patients.