What ingredient may I be allergic to in certain beers? Mandatory disclaimer: I'm not asking for health related advices, this question is just out of pure curiosity.

I drink the occasional beer, wine, or whatever other alcoholic drinks: no issues with that, not getting drunk with just a beer, etc. etc. But...since I have memory, a single red beer can put me under the table.

From the next day. (yeah, not the same day)

With lot of stomach and intestinal pain and "funny" side effects.

And a few days needed to recover.

Now, it's not a big deal: on my list of things to avoid "Red beer" has been put in the top 5, and problem solved. It doesn't happen with 100% of the reds, but at 95% occurrence I just play safe...plus I prefer dark beers anyway :-D

Only, exactly one week ago I got the same amazing effects, but worst, and I'm still halfway from full recovery...from a bock. Ok, "bock" is a pretty wide definition, but while I'm not an expert on beers I've always been pretty certain that if I order a bock I never feel bad the next day.

So now I'm extremely curious to understand what it may be to knock me down this way, but as I said I'm no expert and that's the reason I'm asking here.

Question: What 95% of red beers and a Scheyern Kloster Doppelbock Dunkel (Poculator) have in common, in terms of ingredients and/or preparation?

(bonus: I get the same effect with some Scotch)
Sounds like allergy to

malted barley or other grains, such as wheat and sorghum
hops
yeast
assorted colorings, flavorings, and preservatives

Can you eat rye normally?