My guess: candida. It lives in the intestines, frequently becomes systemic, grows out of control and aggrivates the body's immunities, resulting in allergies. I have suffered from this for decades and am only now starting to get it under control. Alcohol (particularly the yeasts in beer) feed the candida and intensify symptoms. So will sugars and carbs (does he crave these things?). It doesn't mean he has to give up alcohol (I haven't) but some steps should be taken. Check out the Candida Forum on Curezone.