Ive seen people with the crappiest diets have gorgeous skin, and those who eat clean with severe acne. Back in the dark ages when i first got acne (early 70s), doctors still subscribed to the diet-causes-acne philosophy...probably because they had little else to offer. I was put on elimination diets until i was practically eating nothing, and none of it helped. I spent (wasted) months doing it.
Acne has always been with humans. Early literature mentions it, in every culture, in every era. It's caused by a defect in cell structure, over-productive oil glands, and bacteria. You need all 3 of those things. All the liver-stimulating garlic or Tibetan virgin clay in the world won't help you if you have the perfect storm of acne causers.
I have suffered with acne for 40 years now...i have tried it ALL...and i contue the struggle, even at age 50. For someone to come in here and say clay or diet cures it is ridiculous. Acne is complicated and horridly difficult to treat. There are no easy answers, but if someone tells me they've been struggling for years, i tell them to see a doctor, because they've probably already tried all the obvious suggestions for mild acne and it's time for serious medicine.