Hey did you find the cause and/or cure for this problem? Your symptoms sound extremely familiar to me as I am experiencing very similar phenomen that is slightly itchy during the day but kicks into overdrive as it gets darker in my room. Keeping the light on lessens the intensity but is still quite unpleasant to say the least and I've noticed a lot more hair shed in the shower and in my sheets due to the scratching.
I'm scratching my beard area raw and afraid I'm going to get permanent hair loss. If you get a cure I'd really like to hear about it! Personally, I'm having a problem receiving medical treatment right now and have to look for a new place to get care where they will not just blow me off.