A few of the putative anti-migraine drugs are antihistamines. (Esp. H3 and H4.) But there's still no evidence they actually work.

Relating anything to diet is somewhat silly at this point as there's enough cases with wildly varying diets. It's a great way to sell a quack treatment though.

Yes. I have yet to find a diet that quells the attacks unfortunately. I had hope it might be sodium related, but cutting it out of my diet (mostly) had no noticeable effect.