Draught vs. bottled beer

Factual Questions
1

I’ve spent hours looking for the answer to this question, with no luck. It seems like the kind of question someone must have asked before, and I think that someone here will know (or link me to) the answer.

Here’s the question: Why is it that I am more likely to get a headache from drinking bottled beer than draught?

First of all, I’m not talking about hangovers, per se. I’m saying that I can drink one or two pints of draught (occasionally I’ll even have a third), and feel fine. But - often when I have one or two 12-oz. bottles of beer, within an hour or so I’ll get a splitting headache.

Second point of clarification: I don’t drink “macrobrews”. I’m talking about microbrews, and my preference tends toward amber ales - medium hoppiness. But it doesn’t happen with just one type, and it can even happen with the same beer (the bottled version giving me a headache when the draught version doesn’t, I mean).

Is there something (like the pasteurization, or addition of preservatives) that happens in the bottling process that is causing this?

Thanks.

2

Might temperature be a factor (i.e. like an ice cream headache)? Bottled beer is often stored in a refrigerator; most fridges are kept only a few degrees above freezing (usually 35-40 F), while kegs are usually kept a bit warmer.

AFAIK, keg beer is the same stuff that gets put into bottles (except possibly Guinness Stout), so I don’t think preservatives are an issue.

3

Interesting. Most bottled beer is pasteurized by heat, whereas most keg beer, at least in the US, is pasteurized by filtering. Maybe there is some byproduct generated by the heat process that gives you a headache? Can’t guess what, but I’ll think about it.

Many draft and bottled versions of the same beer are actually different BTW. The alcohol content can vary, for one thing.