I've had acne for about four years now, since I was 15. Years ago, I used to get acne on both my cheeks and my forehead area. My acne has always been pretty much mild, I usually only have 1 - 2 moderate sized pimples on my face at a time. If it's a bad breakout maybe 4.
However, now, it seems that my acne's changed. I rarely break out on my forehead anymore. The last time I had a pimple there was five months ago, and before that pimple, the last one was five months before as well. In the past three months, I also have not gotten ANY pimples on my right cheek at all. Only my left cheek has gotten pimples.
Even my derm pointed it out, saying "Have you noticed you only get acne on one side?" I have no idea what could cause this. I have an acne routine - I'm taking Minocycline (but going to switch back to doxy soon) and use Epiduo at night. I take Fish Oil, Vitamin D, and Zinc supplements. I wash my face thoroughly twice a day and moisturize twice a day. I keep my hair out of my face and almost never touch my face. I never touch my phone to my face. I try as hard as I can to either sleep on my back OR on my right side, so only my right cheek touches the pillow. What could be causing this??
Check out acne face maps. Ancient medicine (Chinese) maps the face and explains which parts of the face correspond with parts of the body. I'm not sure how accurate this is but it's pretty well respected and many acne.org users have found it useful and truthful in terms of their own acne. Look one up online.
People aren't symmetrical. I've noticed that I have more acne/hair/freckles/fine lines in certain parts of my body on one side more than the other.
Right now I tend to get a little acne on the right side of my forehead, the left side below my nose, the right side of my nose. I don't think you're going to find a reason why this happens (aside from instances where someone touches a certain part of their face a lot, for whatever reason).
The only advice I can give is, sometimes when I get an area where acne keeps coming back, the only way to get rid of it is to use Neosporin for a few days. You could try that.