I get red bumps on my face and back that itch. What is it?

I also get them on my scalp. I first started getting them on my scalp and went to the doctor and they cut one off and tested it and didn't know what they were. Now I get them on my scalp, face and back. They look like a bug bite or hives. I thought it was coming from stress but even when I don't feel stressed they still come. I have tried benedryl gel on my face but it only works for the itch for short period of time. They itch so bad sometimes I itch them to the point where they turn into sores. Please tell me what they are and what I can use to get rid of them permanently.