Interesting stuff. I get the tinitus occasionally... I think it's very much vascular (high blood flow or inflammation around the veins causing turbulent flow near the ear - probably the latter).

The antihistamine might be majorly responsible for that - though melatonin effects a couple different neurochemicals (I can't remember off the top of my head but I know seretonin is one)... pretty sure antihistamines have an effect on inflammation.

Thanks for the information! I might have to look into all of that.