Sometimes hairline Acne is due to not rinsing shampoo and facial products thoroughly enough in that area; we tend to neglect the hairline, so make sure there is NO residue left there to cause a break-out.
What's worked for me is:
-Anti-candida/yeast products from the health food store
-Apple cider vinegar (fights oil and yeast) taken internally, google for more info
-"bikini-zone" anti-bump after shaving gel; it is excellent for fighting the bacteria that causes razor bumps and I tried it on pimples where it was more effective than any Acne medication I ever tried.
-Carrot juice for the vitamin A that skin needs badly. Good luck.