Why do bud products cause headaches?

my husband drinks on average 1-2 beers a day. Sometimes he will go a few days without drinking at all, some weekends he will drink several. HE NEVER HAS A HANGOVER. He has been drinking Natty's because ALL budweiser products have been giving him excrutiating headaches (migraines with mild sensitivity to light and sound) I have migraines so I know...(I do NOT drink at all) he drinks not even 1/2 of a bud light and he curls up with a migraine, he takes 2 advil liquigels and a nap and hes ok. Bud Ice makes him feel "like his heads going to explode". Any explanations?