Hello,
The acne on head can be due to folliculitis or perifolliculitis. Eat a healthy diet. You can also take vit B6 and vit A and E which are good for hair and skin. Try medicated shampoos for dandruff. There are a number of over-the-counter shampoos available that can help. The most effective ingredients -- antimicrobials -- to look for are zinc pyridinethione, selenium sulfide, sulfur and ketoconazole (also available by prescription). If your hair is colored, don't use products with selenium sulfide or sulfur.
For folliculitis, you may need topical and oral antimicrobials for which I suggest you to get it examined from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
There are many over the counter anti dandruff shampoos. Selsen Blue is one of them. If your hair is naturally too oily, try a shampoo the says "clarifying" . A lot of these type of shampoos help at the root of the hair shaft and help balance out the amount of moisture present. I have a teenage daughter with this exact problem. I ended up buying a clarifying shampoo from a local beauty salon. Not cheap ($13 for a bottle) but it kept her from getting that oily hair that was exacerbating her acne on her forehead, hairline and anywhere her hair touched. If anyone knows of a less expensive way, I like to know too.