the itching is called the robo-itch and is usually caused by the inactive ingredients in dxm medicines, and panic and paranoia is a sign of a bad trip usually. only a very small minority of people have a alergy to dxm, actually its more of a liver enzyme deficiency so the dxm isnt broken down resulting in poisoning, for some reason caucasians are more likely to have this deficiency but even in them its a extremely small percent.