Since hair has NO pain receptors, it is probably your scalp that is feeling 'irritated'. If it's really bothersome, I'd first see a general practice MD..and go from there. IF you have tried lots of shampoos, you may have dried your scalp out to the point of it feeling like it is.
I do know this, I am normal and healthy, but since i was a child, if change the area where my hair is parted on my head, WITHOUT WASHING MY HAIR, I get terrible sensitive pain on my scalp and a BAD headache...almost like a migraine. I just never change my part without shampooing.
Hope it helps.
thanks for taking time to reply