Acne is the most common skin disorder in the world. It affects the hair follicles and the glands that produce skin oil (sebum). Clogs in the follicles can cause the buildup of sebum, which may lead to infection and inflammation. Acne is most common in teenagers, but may affect people of any age. Although acne typically goes away by age 30, it may persist much longer.

There are many types of acne. The common form is acne vulgaris, which may be classified according to severity and risk of scarring.

The overproduction of skin oil, irregular shedding of dead skin cells, buildup of skin bacteria and inflammation or infection may all contribute to the development of acne. The cause of these contributors and of acne in general is not known. However, hormonal changes (e.g., puberty, menstruation), family history, allergies, certain chemicals or substances (e.g., chlorine, tar, grease) and other factors are also involved.

Acne lesions include whiteheads, blackheads, pimples, cysts and nodules. They may occur anywhere on the body but are most common on the face, neck, chest, shoulders and upper back. These lesions may leave a variety of different scars, from tiny, deep holes (“ice pick” scars) to large, irregular indentations (“box car” scars).

The diagnosis of acne is usually obvious. Treatment aims to minimize scarring, prevent further blemishes and improve those already present. Treatment may be topical or systemic. The first line of treatment is typically over–the–counter, topical treatments. If these are not effective, the dermatologist may prescribe stronger topical treatments (e.g., retinoids, antibiotics). Oral antibiotics may be used in cases of moderate to severe acne.

Acne scars may be treated by a number of procedures that remove damaged skin and promote growth of new, smoother skin. These include dermabrasion and laser resurfacing. Other physical methods of treating acne scars involve loosening or filling the skin beneath the scar and the surgical removal of the scar.

Acne outbreaks and the worsening of current acne may be prevented by gently washing (not scrubbing) the problem area twice a day, keeping the hair clean, not resting hands and objects (e.g., telephone receivers) on the face, refraining from picking or squeezing current blemishes and shaving carefully to avoid irritating blemishes.