Alcohol and allergy meds

I googled it and apparently you can’t mix these. I was just wondering if anyone here knew why?

I’m not planning to drink while taking my allergy meds but I just wasn’t sure why the mix is bad enough it actually shows up on google. Bc I know you shouldn’t have alcohol while taking cough medicine but it doesn’t seem to show up on google, I just know from other people not to mix cough meds and alcohol. Wasn’t sure why alcohol and allergy meds are so bad. I have Reactine for some skin issues but I feel like I can’t take it when I should be bc I’m an alcoholic

I would’ve asked this in an allergy subreddit but I can’t find a general one to ask this in