What causes acne?
Acne occurs when hair follicles (the "pore" or hole in which a hair is rooted) becomes clogged with dead skin and oils (oils are produced by an oil gland within the hair follicle).

A clogged hair follicle can remain closed to the outside and appear white at the tip (a "whitehead") or can open up to the air and become darkened (a "blackhead").

When hair follicles become clogged and debris collects, they can become infected with a bacteria called P. acnes. This bacteria normally lives on the surface of the skin in small numbers and does not cause problems unless it starts to grow inside the plugged hair follicles.

"Pimples" and "pustules" are, basically, whiteheads or blackheads that have become infected.

What are the different phases of acne?
Whiteheads are clogged pores that have not opened-up; Blackheads are clogged pores/hair follicles that have opened-up and darkened; pimples are red, raised spots that are infected/inflamed; pustules are pus-filled pimples; cysts are thick, firm lumps beneath the skin where secretions/debris have built-up within the pores.

In early stage acne (comedonal acne) whiteheads and blackheads are present. With "mid-stage" acne (mild inflammatory acne), pimples are present, indicating inflamed/infected pores. With final phase acne (moderate to severe inflammatory acne), pimples and pustules (pus-filled pimples) increase in number and may cover much of the face and upper body as well. Cysts (deep, painful, pus-filled bumps) develop in a small percentage of individuals and require special care so that they do not leave scars.

Most people with acne have inflammatory acne, with pimples, pustules, whiteheads and blackheads on their face and upper body.

Is my acne mild, moderate, or severe?
Experts use a complex method to rate acne severity that involves counting the different types of blemishes (whiteheads/blackheads, pimples/pustules, and cysts) on the face and body. Many different rating scales have been developed. The following is a commonly used scale:

Mild acne:

Less than 20 comedones (whiteheads/blackheads), or

Less than 15 papules (pimples/pustules), or

Total blemish count (any type) of less than 30.

Moderate acne:

15 to 20 papules (pimples/pustules), with comedones (whiteheads/blackheads), and rare cysts (deep, painful, pus-filled bumps), or

Total blemish count (any type) of 30 to 125.

Severe acne:

Inflamed nodules (lumps) and cysts (deep, painful, pus-filled bumps), with comedones (whiteheads/blackheads) and papules (pimples/pustules), or

Total blemish count (any type) of more than 125.

Why is overuse of antibiotics a problem?
Antibiotics improve acne by fighting the bacteria that infect pimples. When antibiotics are used for long periods of time, the bacteria "learn" to alter/change themselves (develop "resistance") so that they can survive in the presence of the antibiotics. Too much exposure to antibiotics leads to bacteria that are no longer treatable with antibiotics.

With the development of widespread bacterial resistance, severe acne has become more common, and people with acne must resort to using increasingly powerful medications that can cause many side effects.

To decrease the development of bacterial resistance in any one individual or for all acne-sufferers, in general, experts recommend using antibiotics for relatively short periods of time, and treating, long-term, with other types of acne medications.