My Skin Itch And Raised Red Bumps Appear That Are

My skin itch and raised red bumps appear that are grouped. They only appear when I scratch. These bumps appear mostly on my lower back and the back of my arms and shoulders. I've had some itching on my wrist, leg, and thighs where it turns red when I scratch and bumps appear. The ones on my shoulder have gotten better and are less itchy. I did some lawn work a week ago. I picked up a stingy bush and stuck my finger and raked up pinestraw and the day afterwards these symptoms appeared. What do I have?