Migraines can cause your stomach to empty too slowly, making you feel like shit:
Gastric stasis, also called gastroparesis (5), is defined
as delayed emptying of the stomach in the absence of mechanical obstruction, and its clinical manifestations include nausea, vomiting, bloating, and weight loss (6).
In addition to making you feel even more awful than a migraine generally makes you feel, it can stop your triptans from working.
Oral triptans are not the optimal therapy in the presence of migraine-related
nausea because nausea predicts poor response to oral triptans and
because nausea can cause patients to delay oral treatment, which can
further compromise therapeutic efficacy. Oral triptans are not the
optimal therapy in the presence of migraine-associated gastroparesis
because these agents rely on gastric motility and gastrointestinal
absorption and may be ineffective or slowly or inconsistently effective
in the presence of gastroparesis. [link]
Maybe migraines fuck up your stomach because migraine is an ANS disorder?
It is hypothesized that both migraine and GS arise
because of autonomic nervous system (ANS) dysfunc- tion (13–16). Gastric stasis during migraine may be attributed to increased sympathetic nervous system activity, decreased parasympathetic nervous system activity, or both (4).
This paper is pretty similar to another by S.K. Aurora that I mentioned the other day, but has a little more detail.