You can have acne on any region of your body. Because your scalp is made of skin, which is what acne affects, it is an area where acne can be and are found.

When a pore or hair follicle becomes blocked with dead skin cells or sebum, the natural oil the skin produces to keep itself hydrated, pimples on the scalp develop much like they do elsewhere. Another thing that can enter the pores and trigger a reaction is bacteria, yeast, or mites. There are many oil glands and hair follicles on your scalp. Acne may result from a pore or follicle becoming clogged with oil and debris. Even if you practise adequate hygiene, you might still get scalp acne because sweat, oil, and grime accumulation from improper or insufficient cleaning can result in clogged pores.

It's troublesome, of course, so be gentle and hopefully your doctor can make some practical suggestions for you to tackle this safely. This is especially true if it's chronic acne. Chronic acne may require medication, and it may even require a specialised shampoo to help treat your scalp. In the meantime, use a soft brush on your hair so you don't disturb the skin on your scalp too much.