No one factor causes acne. Acne occurs when sebaceous (oil) glands attached to the hair follicles are stimulated at the time of puberty or due to other hormonal changes. Sebum (oil) is a natural substance that lubricates and protects the skin. Associated with increased oil production is a change in the manner in which the skin cells mature, predisposing them to plug the follicular pore. The plug can appear as a whitehead if it is covered by a thin layer of skin, or if exposed to the air, the darker exposed portion of the plug is called a "blackhead." The plugged hair follicle gradually enlarges, producing a bump. As the follicle enlarges, the wall may rupture, allowing irritating substances and normal skin bacteria access into the deeper layers of the skin, ultimately producing inflammation. Inflammation near the skin's surface produces a pustule; deeper inflammation results in a papule (pimple); if the inflammation is deeper still, it forms a cyst.
Another study focused in on dairy. In 2005, an article in the Journal of the American Academy of Dermatology took on milk and milk products. By examining the diets of 47,355 women, researchers observed a significant connection between milk and dairy intake and breakouts. Some researchers believe this is caused by high levels of hormones found in our milk products. Much of the milk consumed is produced by pregnant cows, who pump out progesterone, IGF-1, and other compounds that are then passed into the milk. We may also be subject to Bovine Growth Hormone (BGH). These hormones can signal the oil glands to start producing more sebum, which can affect acne. Unfortunately, switching to organic milk doesn’t seem to make a difference, and neither do skim milk options. In fact, skim milk has been observed to worsen the skin, which researches have attributed to lower levels of estrogen and different processing activities. Milk is also known to contain a number of vitamins, some good and some not so beneficial to your skin. Research has shown a correlation between acne and vitamin A in milk.
Acne (acne vulgaris, common acne) is a disease of the hair follicles of the face, chest, and back that affects almost all teenagers during puberty -- the only exception being members of a few primitive Neolithic tribes living in isolation. It is not caused by bacteria, although bacteria play a role in its development. It is not unusual for some women to develop acne in their mid- to late-20s.