Acne is a disease that affects the pilosebaceous unit. It is characterized by the appearance of comedones, papules, pustules, and cysts.
These usually appear on the face and upper part of the trunk, where there is a higher concentration of sebaceous glands.
There are four main factors that cause acne:
1. Excessive production of fat
2. Obstruction of hair follicles with fat and dead skin cells
3. Bacteria
4. Excess activity of one type of hormones (androgens)