What Causes Itchy And Painful Bites On Arms And Shoulders?

this is the issue - i have what looks like small bites on my shoulders and arms just a few on my neck - they itch and get larger look like welts - this has been the case for the last 2 years - have been to 7 different physicians, inclusive of Dermatologists (and the best in my area of Philadelphia) I have a litany of creams that were given via prescription, have spent considerable money and I still have bites (worse at night) itching and somewhat painful - what do you have to say?