I believe it is hormonal. I strongly believe that. Much of what I have read (and I have read A LOT!! lol)about acne, the location of acne, etc. indicates that acne along the jawline and chin is hormonal. When I break out before my period starts, it is ALWAYS in that area. Someone would have a hard time convincing me otherwise. Now I'm not saying that other things cannot cause breakouts in that area. I'm saying that hormones play a very significant role in breakouts in the chin/jawline area, IMO.
I have been taking 3 separate supplements: saw palmetto, b-complex vitamin, and zinc. That combo has cleared up 99% of my chest acne, which I am told is also related to hormones. So, I'm gonna give that combination time to work on my chin/jawline. From what I'm told, it could take a few months for it to really work on the face. Even though my chin and jawline only breakout before my period, I'm hoping those 3 supplements will keep the breakouts to a minimum.