The most common causes of acne include: bacteria, clogged pores, triggers, cosmetics or skin care products. Clogged pores happen due to old skin cells that are still on the skin. Whether someone is not using a mild scrub to eliminate the excess skin cells, or the subject has Retention Hyperkeratosis where your skin cells replicate very fast, the outcome is the same. With these extra skin cells on your face, and then the mixture of sebum...