I too have had this itch on my arms. It is like a thousand fire ants under my skin. I did find a pain pen called Flex24 that relieves it immediately. You can by this online for about $9.
I also have this itch and its awful, Ive found out that capsaicin just a little on the itchy area and around it works. Be carful because its like a heat rub so wash your hands and be carful what you touch but it really helps me and my itch is horrible sometimes. from what I understand the cream kills or deadens the nerves under the skin.
Sounds like Brachioradial Pruritus. There's a whole forum on it under 'dermatology' here. I think it's posted under Itchy arms=brachioradial pruritus. If indeed you have BRP, my extensive research shows it's actually caused by nerve damage/compression of the nerve roots from the cervical spine (typically C4-C6). Topical ointments, ice, etc. only over-ride the nerve impulse causing the itch for a short time....if the compression and consequently the inflammation responsible for the neurogenic itch isn't resolved, the itch continues. It's often worse in the summer with the heat and sun due to increasing the internal inflammation. Anyway, good luck to you! I've had this condition for about 14-15 years myself....mostly resolved, but any change in activity or re-injury to the area and my itching comes back. I truly hope you can find out truly what is causing your itching and if it is BRP, get it resolved =)