Have you changed your shampoo or conditioner, or any hair products lately? I used to get pimples on my scalp when I used hair gel. Stopped using it, they disappeared. I'm very sensitive to certain things, and I can't use any kind of OTC hair conditioner, only coconut oil. Anything other than shampoo that I put on my head makes me get pimples on my scalp, then I want to pop them, and they scab over. If I pick at them, they bleed. It could be parasites, or as simple as a reaction to your hair care products.