The stomach issues started gradually after I'd taken MSM for about a month. I kept getting these mild stomach aches. I didn't connect them to the MSM and I kept plodding forward. I had a hair analysis that showed I was extraordinarily low on sulphur, so I assumed I should continue. But the stomach pains progressed to burning pain, and then eventually I was doubled-over with what felt like acid burning a hole through my stomach. My doctor told me it was actually low stomach acid, and after reading about that, I discovered that low stomach acid can be a sign of thyroid dysfunction. I discovered that if I started taking my thyroid meds again, the stomach pains lessened. And eventually stopped.
That took care of the burning acid pain. But my digestion was just completely halted. No stomach sounds or activity, and I constantly felt bound up.
Histamines are involved in release of hydrochloric acid. I eventually found a site that said alpha-methyl-histamines stop the release of hydrochloric acid. That's when I started researching methylation and folic acid.
Histamines are also involved in wakefulness. Histamines on - wakefulness. Histamines off - fatigue/drowsiness.