Bumpy Rash

I have this weird rash that comes and goes. It's almost as though something is biting me, but it happens when I'm walking around so I don't think anything is. It's mostly on my forearms. They start itching and then a whole bunch of little bumps appear. They spread down my arm as does the itching. They are always skin color and go away in about 10 mins. Does anyone have any idea what this could be?

Also, my son's butt at the very top as been itching him. Every time he scratches there's nothing on his skin. We've tried treating it with Lotriman (antifungal) and hydrocortisone. Nothing seems to stop the itching either? There are no bumps nor any skin discoloration. Not sure if this is related to my itching, but it's very weird we're all itching like this at the same time?

Any help would be appreciated!

Thanks,
Jennifer