I've suffered from acne since age 13 (now 26). I finally decided to seek professional help from a Naturopath in Feb 2017. The doctor suggested 3 tests: a GI Map stool test for gut issues ($180), a nutrient deficiency blood test ($180), and a food sensitivity blood test ($600). I opted for the most expensive food test, but there are cheaper ones that test fewer foods. I did all 3 tests and had all results in about 3 weeks.

The nutrient deficiency testresults showed that i was deficient in D3, B12, K2, and a few other things.
The food sensitivity test showed that i was severely sensitive to about a dozen foods, moderately sensitive to about 20 foods, and mildly sensitive to another 20 or so.
Most importantly, The GI Map test showed that i had a high amount ofCitrobacter Freundii in my gut.

The doctor explained to me thatCitrobacter Freundii can be caused by long-term antiobiotic use. I had taken Doryx for over a year in my teens, so this made sense. My treatment plan has been extreme but effective. My face has improved by 90%. I'm using the Acne.org regimen morning and night, mixing in AHA with the moisturizer twice a week to exfoliate. Also, it's been my experience that the Acne.org recommendation of cleansing for only 10 seconds is not enough. I do it 30 seconds and do a double cleanse at night. Anyways, here's the effective treatment plan that i've been following:

Supplementation (in order of importance):
Thorne Research Formula SF722 10-Undecenoic Acid 250mg
garden of life probiotics 90 billion
Oreganol 140mg
Ortho Molecular Products Liquid d3 + k2
Klaire Labs Interfase Plus
GI Microb-X
Vitamin Code Raw K Complex
Vitamin Code Raw Zinc + Vit C
Olive Leaf Extract

Diet:
Extremely low sugar, gluten-free, no dairy, mostly organic.
Organic almond butter (almonds should be the only ingredient)
Food for life gluten-free english muffins with almond butter and organic Cinnamon
Food for life gluten-free organic breadwith almond butter and organic Cinnamon
Organic black bean spaghetti withOrganic olive oil, organic flax meal, pink salt
Organic almond milk
Organic Avacados
Wild caught Salmon
Organic carrots & organic Asparagus

I would suggest that anyone suffering with adult acne see a naturopathic doctor.