For the past three years, I have been an incredibly hard drinker. I could easily drink the better part of a liter of vodka, not be sick, and wake up the next day with a managable hangover. About three months ago, this all changed suddenly. Now whenever I have more than two beers, I wake up the next morning violently ill. I have frequent heartburn, constant nausea, and itchy skin if I have had any alcohol in the past 24 hours. Have I developed an allergy to alcohol? I’ve tried only drinking beer, or wine, or liqour to see if it was a particular kind, but they all make me feel wretched. What does this mean?