Acne typically appears on your face, neck, chest, back and shoulders, which are the areas of your skin with the largest number of functional oil glands. Acne can take the following forms:

Noninflammatory lesions

  • Comedones (whiteheads and blackheads) are created when the openings of hair follicles become clogged and blocked with oil secretions, dead skin cells and sometimes bacteria. When comedones (koe-muh-DOE-neez) are open at the skin surface, they're called blackheads because of the dark appearance of the plugs in the hair follicles. When comedones are closed, they're called whiteheads — slightly raised, skin-colored bumps.

Inflammatory lesions

  • Papules are small raised bumps that signal inflammation or infection in the hair follicles. Papules may be red and tender.
  • Pustules (pimples) are red, tender bumps with white pus at their tips.
  • Nodules are large, solid, painful lumps beneath the surface of the skin. They're formed by the buildup of secretions deep within hair follicles.
  • Cysts are painful, pus-filled lumps beneath the surface of the skin. These boil-like infections can cause scars.

When to see a doctor

Acne usually isn't a serious medical condition. But you may want to seek medical treatment from a dermatologist for persistent pimples or inflamed cysts to avoid scarring or other damage to your skin. If acne and the scars it may have left are affecting your social relationships or self-esteem, you may also want to ask a dermatologist if your acne can be controlled or if your scars can be diminished.

Oct. 21, 2011

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