I Pulled Weeds From Garden 2 Wks Ago;itching, Welts, Red

I pulled weeds from garden 2 wks ago;itching, welts, red skin areas started on chin, last week more welts & rash on body the last 5 days; used cortisone cream 1%; pharmacy suggested diphenhydramine hydrochloride 2%; no better. Think it's a reaction to weeds I pulled out? could it be shingles? Poison Zumack?