What Causes Recurring Acne At The Base Of Skull And Neck?

I've been having recurring heavy acne at the base of my skull, back of neck area just above the hairline. I do tend to have oily skin and hair but I wash my hair every day and wonder why the acne would be concentrated in that area just above the hairline. I've seen references to acne bacteria made worse by problems with incomplete digestion and/or liver problems.