People who cannot tolerate alcohol may have a genetic
error of metabolism:

http://everything2.com/title/alcohol%2520intolerance

If it is only beer, then I would seriously explore gluten intolerance. This can cause all sorts of neurological problems:

http://jccglutenfree.googlepages.com/

People with severe anxiety that does not respond well to medications may have a condition called pyroluria. It can cause many alarming mood swings, and is due to a low level of B6 and zinc in the body. It is easily tested for and treated.
http://www.drkaslow.com/html/pyroluria.html

There are people who have genetic differences in how they
metabolize drugs. Since you are posting about this, I'd get the DNA testing done so you will KNOW for sure if you have this.
examples:
http://www.healthanddna.com/healthca...enotyping.html

This chart shows occurance values for various ethnic groups:
http://www.genemedrx.com/CYP450Table.php

http://www.jpnonline.com/view.asp?rID=24226

https://www.dnadirect.com/profession...e/why_test.jsp

People vary in how they metabolize drugs and other substances that they consume. If you have unusual responses then it would be best to find out why.
This testing could save alot of grief and suffering down the road for you.