alcohol is an organic solvent and dissolves cell membranes. it is a poison, essentially. I stopped drinking it when I was 23, once I realized what it was. re-read your list of symptoms after drinking it and realize what you are describing: poisoning. some people can tolerate it and some can't at all. if I have just one sip I turn into a zombie. some types of alcohol contain tyramine, like red wine, and you are describing tyramine poisoning with the sudden headache.
it is a characteristic of people who are chemically sensitive to also be intolerant to alcohol. I have known many people on these boards and those who have completed the QEESI test have all been positive for chemical sensitivity. it seems to me that chemical sensitivity is part of IIH, whether most of us here realize it or not. we are all environmentally sensitive in one way or another, but I suspect that our sensitivity to chemicals plays a role in the IIH. keep in mind this is all just my theories about it after observing us for years. but some develop IIH after exposure to certain medications. what if a pesticide we are exposed to but can't prove it, does the same thing? the illness model for medication induced IIH and that for MCS are the same. anyway, all that to say that I think there probably is a relationship between IIH and alcohol intolerance. I just don't know exactly what it is.