Alcohol allergy? Really? So rare, and set off by drinking alcohol, not by proximity to someone else drinking.
People who are so hysterical about their allergies that they want to restrict everyone else ought to get their doctor to prescribe a "pulse" of steroids and antihistamines to protect them during their flight. After all, a life threatening reaction at 35,000 feet over the ocean is nothing to be, er, sneezed at. Better not to take ANY chances.
Anyone who demands to have restrictions placed on an entire aircraft should be required to produce a recent letter from a board-certified allergist attesting to the need for such. Put up or shut up.
I know that there are people with severe allergies who are at risk for anaphylaxis. I even know one, but he does not demand a "peanut-free" travel experience. He knows how to deal with his problem and minimize his risk. I contend that most of these peanut-free demands are made by people who just want to draw attention to themselves.