I sometimes got dizzy with the 2% minoxidil but never once with the kirkland 5% off ebay.
Being off minoxidil for a few weeks there's definitely a general well being that was not present when using it, I felt out of breath easier and the skin on the face was definitely harsher although I can't say if it was related to collagen being inhibit or if it was the vellus being longer. Also I always felt an itch around the eye sockets, don't know if it was irritation from the alcohol in the liquid version.
I've never felt itch on the scalp or irritation, was almost an year on it.