Understanding Acne

A normal follicle, often called a pore, looks like this. The sebaceous glands secrete sebum, an oily substance that coats the skin to maintain hydration. Sebum production increases significantly during puberty and contributes to the development of acne.

Follicles can become blocked by a mixture of dead skin cells and sebum, which forms a microcomedone. Much of the sebum that normally flows out of the follicle onto to the surface of the skin is trapped inside the follicle. Proprionobacterium acnes (P. acnes), an anaerobic bacteria that normally lives on the skin, thrive in this environment. Lack of oxygen and plenty of sebum to feed on allow them to flourish. At this stage the blockage is invisible to the eye and may take as long as eight to ten weeks to develop into a visible blemish. Both whiteheads and blackheads start out as microcomedones.

Residue from makeup can also create this initial blockage and lead to cosmetic acne. Regardless of the cause of the initial blockage, the results are the same.

As the plug becomes larger and more fully blocks the pore opening, it changes from a microcomedone to a comedone. If the comedone is open to the air (referred to as an open comedone), the melanin (skin pigment) in the dead skin cells oxidizes and becomes dark in color, forming a blackhead. The oxidized melanin is not dirt or makeup and cannot be washed away.

If the comedone forms beneath the surface of the skin and is closed to the outside air (referred to as a closed comedone), it does not oxidize and forms a whitehead. At this stage, the acne is non-inflammatory. The blackheads or whiteheads can release their contents to the surface of the skin and heal without causing an immune system response.

Comedones often contain debris that is deep and impacted, which can lead to inflammation and the formation of a papule or pustule. Papules appear when enzymes released by P. acnes bacteria break down sebum into free fatty acids that irritate the follicle wall.

Pustules occur when the immune system responds to an active P. acnes infection within the follicle and white blood cells make their way to the surface of the skin. This is what people usually refer to as a zit or pimple.

An inflamed lesion can sometimes rupture, causing inflammation to the surrounding skin. These lesions are called nodules or cysts. The rupture can be caused by random occurrence or by touching or picking at the skin. This is why it is important to leave acne prone skin relatively untouched.

When a follicle breaks along the bottom, total collapse can occur, causing a large, inflamed cyst that can be sore to the touch. The cyst has no passage to the surface of the skin so touching or squeezing it causes it to become larger and more inflamed. Because it affects deeper layers of the skin, cystic acne frequently causes scarring.

Milia are not acne but are white bumps that form when skin cells become trapped in small pockets on the surface of the skin rather than exfoliate naturally. The trapped cells become walled off into tiny cysts that appear like white beads below the surface of the skin. Milia can occur on the skin, mucous membranes such as the inner surface of the cheek, or the vermillion border of the lips. As the skin surface is worn away, the tiny cysts may resolve on their own. Intervention to remove the cyst may offer more rapid resolution.

The most common cause of milia is the use of heavy skin care products. Comedogenic creams and lotions may prevent the sloughing of dead epidermal skin cells. Hidden problem products include makeup removers not labeled oil-free or non-comedogenic, heavy sunscreens, and some moisturizers. The eyelids are very thin and more likely to experience problems with milia due to cosmetics. Milia can also be caused by cumulative sun exposure. Aging skin forms a thicker epidermis that makes it more difficult for skin cells to exfoliate naturally.