Cosmetic ingredients are grades according to their ability to form comedones. This has been a concern for cosmetic formulators for many years. Ingredients that do not cause comedones are said to be non-comedogenic. Comedogenicity or pore clogging is very closely linked to acne. There are numerous forms of acne. The exact cause of acne is unknown. Acne vulgaris is a complex condition involving many factors. The changes that occur in the body around the time of puberty are part of the story. Increased sebum or oil made by the oil glands in the skin on the face, chest and back also plays a role. Acne is often slow to respond to any treatment so try to be patient. Stress can also be a cause of acne. So is caffeine that is found in coffee, tea, iced tea, chocolates, Coca-Cola™ & PepsiCola™ and other soft drinks (except the caffeine-free varieties). So if you are under a lot of stress, go have a cola drink and a chocolate bar, then watch your skin break out. One of the most common forms of acne is known as acne vulgaris.