I am a 45 year old male suffering from chronic hives for 18 months now. I notice that it becomes much more active when I go to sleep or feel sleepy. Can I be allergic to the brain chemicals that induce sleep? Melatonin? or seratonin or adenosine? I m not extremely over weight for my height or body type 5 9 - 200 pounds - muscular build but I may or may not have slight sleep apnea . Can sleep apnea cause hives?