I am a woman in my early 20s, and I have recently found red itchy bumps on the back of my arms. It started in a cluster right under my right shoulder, now it is spreading down both my arm and my back. I don't have and food allergies, nor am I allergic to any insect or plants. The only things I'm allergic to are cat dander, dust, and morphine, there are no cat's at my house, there's dust but I don't think that can do this to my arm, and I haven't taken any morphine.