What Causes Itching All Over The Body Post An Insect Bite?

Hello, I recently was bitten by a fly, had a swollen bite, and a week and a half later got the classic bulleye rash. I ve been on Doxycycline to treat the potential Lyme Disease for exactly a week. Over the past few days, my skin feels so itchy. It s as if my skin is so sensitive that it s itchy or as if I have a lot of sharp pricks all at once. Lotion does not help, so I know it s more internal. Sometimes, the itches feel like nerve itches, but not always. My scalp will itch, or the base of my neck, or my legs, or my back, or sometimes several places at once. What s causing this?