Can anyone explain this?

For a few years I've had a very flakey scalp, it gets really bad and I've been given a gel called xamiol which keepsvitvunder control. A few weeks ago I had to go into hospital for surgery to remove a tumor from inside my spinal column. I was in hospital for around 9 days. While I was in hospital, my head totally cleared up, totally! It was as if I never had a scabby, flakey scalp ever. My 't-zone' is also usually dry and flakey yet in hospital is was quite oily. Within a week of coming home I'm back covered in scabs again. What could be the cause of this? I've been on the same medication etc all the time and I can't think of any reason why it cleared up and then came back