https://www.zwivel.com/blog/acne-scar-treatments/

20161007_zwivel_acnescartreatments

“Acne Scar Treatments: Tried-And-Tested Cosmetic Procedures

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What Causes Acne?

While no one knows exactly what causes acne, according to Dr. Emmy Graber, MBA, founder and president of The Dermatology Institute of Boston, possible sources include hormones, bacteria on the skin, the immune system, oil production, genetics, and stress – or a combination of any or all of these factors. …”