What Causes Itchy Bumps On Arms And Face That Leaves Behind Scar?

Bumps that look like mosquito bites keep appearing on my skin either my arms or face; they itch and are red tone. They go down after a few days, but a scar is left behind. I am sure they are not mosquito bits because it is the winter, so i am not sure what is causing them and how do i get rid of the scars they are leaving behind.