What kind of rash is this?

I woke up with a rash that qwas realativly small a few days ago and I just wrote it off as a allergic reactiona dn went on with my life and it started to go away and then I woke up today and it was coverings most of my inner thighs and the underneaths of my arms. they are large bumps with whjite centers in like clusters except on the arms they are smaller and just red. my family has told me it looks like an allergic reaction or hives but I'm just not sure. they are itchy and spreading slowly but surely. can anyone shine some light on this for me?