What happened

I used to be a social drinker and was good at holding my liquor. One day drank a shot of vodka and threw up instantly. Since that day i get a migraine and feel sick with just a single sip of any alcoholic beverage. I haven’t touched alcohol in 15 years because of it. My liver is perfectly healthy and all standard blood work is normal. What could this be? Could i of developed a allergy or something?