I am now almost certain that acetaldehyde is my migraine trigger. The sources for me included chocolate, alcohol, tomatoes, certain fish and preserved meats, all of which are common sources of acetaldehyde.

I can't always avoid these things, but I can usually avoid combining them, and migraines are now less frequent and a lot milder - unpleasant rather than debilitating.

I have also found that dehydration is a major factor. If I skip breakfast or lunch then I make sure I drink, even if just tea or a large glass of water.