All acne begins with one basic lesion: an enlarged hair follicle plugged with oil, dead skin cells and bacteria. Invisible to the naked eye, blackheads lurk beneath the surface of the skin waiting for the right conditions to grow into an inflamed lesion. As the skin continues to produce more oil, bacteria flourish within the swollen follicle. The surrounding skin becomes increasingly inflamed, as your white blood cells fight against the intruders.

Though all pimples start the same way, they can take on many forms and may react differently for different people. Please note that the following guidelines are not to be used for conclusive self-diagnosis. These definitions may be used to help you decide whether or not you should consider seeking medical attention.

Closed blackheads or whiteheads are plugged follicle that stay below the surface of the skin, and sooner or later appear on the skin as small, white or black bump. A blackhead appears when the plug enlarges and pushes through the surface of the skin. The

Open comedo, or blackhead. If the plug enlarges and pushes through the plug's dark appearance is not due to dirt, but rather to a buildup of melanin, the skin's dark pigment.

The mildest form of inflammatory acne is the papule that appears on the skin as a small, firm pink bump. These can be tender to the touch, and are often considered an intermediary step between non-inflammatory and clearly inflammatory lesions

Like papules, pustules are small round lesions. And unlike papules, they are clearly inflamed and contain visible pus. They may appear red at the base, with a yellowish or whitish center. Pustules do not commonly contain a great deal of bacteria, and inflammation is generally caused by chemical irritation from sebum components, such as fatty free acids.