I've a nasty headache just about every day since Thursday.  Two days ago I noticed it set in immediately after I ate a Hershey's kiss (yes, we're still working through the bag of Halloween candy that everyone brought to lab because they didn't want their kids eating it), and yesterday, I noticed it set in right during seminar (immediately before which, I, of course, ate a chocolate-containing Pepperidge Farm cookie, out of principle.  Out of principle because the department briefly suspended cookies as a cost-saving measure earlier during the economic downturn, so now that they've been reinstated I need to show my appreciation).

Testing the hypothesis that chocolate may be setting off my headaches, I refrained from eating a cookie at journal club today, and I didn't get a headache, consistent with my hypothesis.  (Which of course reminds me of that xkcd cartoon.)  On the other hand, eating a stack of chocolate-containing Hanukkah cookies Monday night didn't make the headache I already had any worse.  Will perhaps try a controlled experiment, but it's tricky because I have only one head.

Other hypotheses include:

1.  Eye strain.  I haven't had a new glasses prescription for three years, and because the glasses I got 3+ years ago have disintegrated, I'm actually using my slightly different prescription from 2003.  Once again, I'm having trouble resolving slides from the back of the room (I normally like to sit up front, but while I was TAing I sat in the back row because I thought it best to save the front seats for actual students), and resolving the names of streets until I'm practically on top of them.  Furthermore, I discovered during the seminar yesterday that vision out of my left eye is much, much blurrier than vision out of my right eye, which assuredly isn't helping.

2.  Scalp strain.  I hear that many headaches are actually caused by scalp pain (as opposed to, say, brain pain).  I haven't had a haircut in about 18 months (my last one was right before Caroline's wedding, in order to look presentable), so the bun that I wad into my hair clip has been getting steadily larger and, therefore, heavier.  Perhaps the tug of the hair in my hair clip is causing headaches.  Letting my hair down after the headache starts isn't enough to cure the headache.  I will get a haircut...sometime when I get around to it.  (Trying to remember how I managed to get regular haircuts when I had short hair.  I guess I just did them when I visited Wisconsin.)