Allergic or just old?

hello. I’m now 25. Have been sort of sober for quite a while (say three four years?) I was never a big drinker, would only just drink at parties and what not(like once or twice a month). Drinking makes me SICK now. One cocktail and I’m throwing up and tapped out. I used to be able to drink liquor like it was nothing/no sickness/no hangover/ nothing. Recently I’ve been having a lot of allergy issues (random hives random swelling) I’ve also been trying to dabble with drinking again. I’m so jealous of my friends who are able to go out out all night and have fun. But recently a single SIP of liquor will make me feel so ill. I really can not hang anymore. Could this be an allergy??? Why am I sick all of the sudden when in the past I could throw back shots like it was water??? Or am I just old ? My roommates and friends are all in their early twenties and I would love to be able to go out with them and have fun. Any advice on how I can keep up would be great. Thank you!!!!