I looked for answers on this board for years and always promised myself if I found something that worked I would sign up and share it, so here it is:

Quick background:
I'm 30 years old, male. I've had mild to moderate acne since I was a teenager, but it flared to severe at age 20 and persisted as moderate acne through to age 30. At different times I tried topical and oral antibiotics, topical retinoid, topical benzoyl peroxide, and salicylic wash.

I even tested a slow carb diet, no sugar diet, and heavy exercise regimen. I could never get my acne all the way to zero, always with 2-6 active pimples on my forehead at a time (my struggle has been mainly with forehead acne).

My solution
After becoming quite frustrated last year, I decided to try a dermatologist one more time, and proceeded to take minocycline and apply tretinoin cream .05%. After 3 months, there was mild improvement, but nothing that I was happy about. So I took one more step and made a few big changes to my diet. The following combination worked tor prevent any new pimples on my forehead for over a month for the first time in years.

• No sugar or fast carbs (white bread, rice, potato)
• Tretinoin cream .05% (I stopped minocycline)
• No dairy (for the first time this meant none- no cream in coffee, butter on toast, and no bread products that even contain milk)

Something was finally working! I was happy to have finally gained control, but I wanted to narrow down to the actual cause. I slowly reintroduced white bread, with no problems. Then some sugars, with no problems. Then finally cheese and milk, and of course I flared up. I even missed certain nights of tretinoin without a problem.

So after half a year of evidence to support this, I want to share that in my case, I believe dairy is the culprit. A big reason it took so long to find out was whenever I thought I was limiting dairy, I probably wasn't (still having butter on toast, having a burrito here and there). It took commitment to have zero dairy, but the change has been dramatic. I hope this solution can help someone who felt as hopeless as I often did.
(I still use the tretinoin in case it helps with scars, but I'm pretty sure that it's not necessary for keeping the acne under control)