A few months ago it felt a bit harder to breathe after taking a few antihistamines. Since then I've gotten more and more sensitive to lower doses and all types of medication, and since the last 2 days I get it without taking any medication at all (except digestive enzymes). I also have an annoying pressure in my head since today. I've had insomnia for some time as well and my IBS is much worse. Could this be some methylation problem? Very thankful for advice.