Itch Skin And When I Scratch Skin Welts Up, Particularly

Itch skin and when I scratch skin welts up, particularly itcy in the evening and any where tight clothes on skin such as bra line. Also notice what looks like rash sometimes when area is scratched. Thought it may have something to do with strawberry patch from a few weeks ago- took some Benadryl but it has continued now for three weeks.
Thank you for your assistance.