itchy arms feel like they are sunburnt and tight

I have suffered for the last 2 years from itchy arms more so when i get warm, but some days my arms feel like they are sunburnt and tight, when they itch i end up with sores and in the hight of the summer i look like i self harm because i am covered in scabs, I have to have a fan on me at night to help to reduce the itch and the bedding ends up with blood on it by the morning where i have scratched myself in my sleep. The G.P has done blood test and said that i am allergic to timmy gress but i am sure there is something else as this goes on all year round. I have had so many antihistamines and steroids and creams but none ever appear to work, the more i touch my arms the worse they are,
at the moment i take 4 allergy relief tablets a day but it does say 1 in 24hrs but i find 2 in the morning and 2 at night does help but i have to keep myself cool, but i look a bit of a fool walking round with my arms uncovered in winter,please could you give me any help???