The mystery is probably the worst part of acne. If I could just figure it out...
I had the same question some 30 years ago at the age of 25 after suffering for 10 long years, week in week out, from the same problem as you and Baroo and Boss 01(there are a couple of pics somewhere on my profile posts) but quite by accident I found the food or should I say chemical additives that 100% caused my huge cystic spots,I still get caught out every couple of years.
I never suffered from common acne,ie lots of small spots ,
So to name a few products that I avoid,which I can say categorically causes my cystic spots are instant soup,rice noodles,gravy/coffee granules,ramen,pot noodles etc,
I don't know the exact chemical but suspect maltodextrin,tricalcuim,dipotassium phosphate,E 150c,E261,E635,E3222,etc,etc,etc.
would like to see your diary of food you are consuming and any medicines as these can contain the same chemicals,
GOOD LUCK,let me know what you think please.