image from @sitthiphong
No one knows for sure what causes migraine headaches. The most likely to answer to-date is that a serious of small irritations or reactions pile up until, finally, a migraine headache is triggered. Migraine triggers are different for each individual, but many migraineurs claim that a particular food or combination of foods will push them over the edge into a headache.
Keep in mind that most science disagrees with migraineurs when it comes to food triggers. There are no conclusive studies indicating a link between certain foods and migraine headaches, so all information is anecdotal. The thing is there is a lot, tons in fact, of anecdotal evidence for the link.
While a migraine trigger food can be, quite literally, anything, some foods come up on the trigger list for enough people to merit discussion.
Cheese is a major trigger for many migraineurs. Particularly likely to cause an attack are hard or aged cheeses. Soft cheeses like cream cheese and new cheeses seem to be fine and unlikely to cause problems.
Nitrates are believed by many to be a major migraine trigger. For most people, the most common source of nitrates is processed meat, items like hot dogs, sausage, bacon, processed lunchmeats, etc.
Salad dressings are a trigger for many. The reason is not known, but is probably tied to a combination of other triggers all coming together in one place.
Spices and Additives
Any spice can be a trigger. Spices as triggers may be tied, at least partially, to scent sensitivity, since many spices have a pungent odor. Seasonings that seem to give migraineurs the most trouble include monosodium glutamate (MSG), common in Asian foods, artificial sweeteners, food dyes, and vinegar.
Migraineurs who suspect a food trigger should consider trying an elimination diet to pinpoint the trigger food(s).