One beer and a headache occurs all day the next day.?!

Best Answer - Chosen by Voters

You may be allergic. Stranger things have happened.

Try freeing up your neck muscles for when they are tight they are the cause of headaches. Your neck muscles go to the top of your head where they connect to muscles going around the head. When the neck muscles get tight they pull on the head muscles and when they go into pain you have your headache. To get rid of it you have to free up your neck muscles and here's how to do that:
Neck
Put your hands alongside your head so your thumbs are on the front of the muscle under your ear and your fingers are on the back of the muscle behind your neck. Squeeze your thumb and fingers together and hold. Relax your body. When your fingers and thumb touch, about two minutes, slowly lower your head as far as you can, release the pressure but hold your neck lowered for another 30 seconds.
For best results relax your body first by taking a deep breath and exhaling then remain this relaxed.