I live in Florida and suffer from the same "itchy arms," and have for several years. No rash
, no bumps, no discoloration - just INTENSE itching on tops and sides from the elbow down. I have never noted whether or not it is seasonal; but it does come and go. I also have psorasis, but not on my arms. In the past I have taken ultra violet light treatments for this condition and have always wondered if that did some type of damage to the nerves in my arms.