I'm not gonna be any help, but if you find out what it is, let me know. I've had something similar crop up within the last week. Red, itchy bumps that appear in clusters. At first maybe I thought it was bug bites, but looking at it now, it doesn't look anything like that. It looks like an allergic reaction. I've got it all over my legs and a couple of small spots on my arms. I made sure I cleaned the house really well, and haven't been eating anything out of the ordinary. And, as far as I know, I'm not allergic to anything. My hydrocortisone cream only keeps the itch away for a small amount of time, and god forbid I touch it on anything, it just starts back up again. D:
My face broke out really bad around the same time, and while it happens around that "time of the month", it's never this bad. I thought maybe it was the dairy I was still eating, but it hasn't cleared up yet. It's like my skin got really angry with me all at once.