I also had same problem for 8 years now, I used different anti-biotics and products, it doesnt help.!!! Only temporary then they keep coming back more agressief.
But now i'm cured of this pimples. i tried almost everything you read here in internet nothing worked for me!
Dermatolog cannot help you. The problem is inside your body.
Care to tell us what your cure was? I for one would be interested since I also experience pimples on my head.