Suggest Treatment For Itching All Over With Pimples

Hi
I am suffering from severe itching problem. It started with my hand especially my arm. It used to start as tiny pimple and it starts itching so bad. Most of my friends have the same problem. I dont know if its the weather or some other issue. In the beginning i thought its the insects causing this problem but now i dont think that is the reason for this itch. Please provide me some medicine and why is it being caused. Thanks