My boyfriend is allergic to alcohol?

Hi guys. So my boyfriend just turned 21, but we’re having an issue with him not being able to have alcohol. He will break out in red hive looking things, gets a mad headache (this is usually the worst part), and ends up needing to sleep it off. He does get pretty bad Asian flush. He’s fully Vietnamese, if that has anything to do with it.

We’ve tried vodka, soju, seltzers, tequila. All have the same effect just at a different level of headache.
Surprisingly he tolerates Cayman Jacks slightly better than the rest?

Do we have to face the fact that he really cannot tolerate alcohol whatsoever? Is it the quality of alcohol? Quantity and spacing? Anything helps.

…And yes I know the “you dont need alcohol to have fun” comments will come, but it sure does help when youre in a a crowded hot club of sweaty strangers lol.