This is what I think I had many years ago when I was pregnant. It was unbearably itchy, on my face and kept me awake at night too. The GP offered no solution except soothing words and in the end I got very cross with him and he stared at me, picked up the phone and made an appointment with a consultant for the next day.
The treatment was a long course of antibiotics but, of course, I couldn't have them until after I had the baby and finished breast-feeding, so I was offered a steroid cream in the meantime. I think it is caused by a staph. infection so mine did need antibiotics unfortunately.
I thought it was hormonal but perhaps it occurs when your immune system is a bit low.