Acne is characterized by an outbreak of lesions on the skin. These lesions include:

• Whiteheads (closed comedones). The openings of the hair follicles become clogged and completely blocked. The soft plug is a white color. These are noninflammatory.
  
  
• Blackheads (open comedones). The openings of the hair follicles become clogged and partially blocked. The plug darkens and is open to the surface of the skin. These are noninflammatory.
  
  
• Pimples (papules and pustules). Raised, reddish spots with white centers that signal inflammation or infection in the follicle. These may be without pus (papules) or may contain pus (pustules). They may be tender or painful.
  
  
• Nodules. Solid, raised reddish bumps.
  
  
• Cysts. Thick lumps beneath the skin formed by the build–up of secretions deep in the hair follicle.

Acne can occur anywhere on the body, but it is most common in areas with high concentrations of sebaceous glands (e.g., face, neck, chest, shoulders, upper back). Mild (superficial) acne is characterized by whiteheads or blackheads and a few small, mildly irritated pimples and usually do not leave scars. Severe (deep, cystic) acne is characterized by many large, painful nodules and cysts that may join together under the skin into even larger abscesses (pus pockets). Severe acne often leaves scars.

Acne scars may last a lifetime or fade over time. They may appear in many forms, including:

• Tiny, deep holes (ice pick scars)
• Wide pits of varying depth
• Large, irregular indentations
• Raised thickened tissue (hypertrophic scars or keloids)

Although over-the-counter acne medications can help treat minor cases of acne, more serious forms of acne require a physician’s attention. Patients should consult with a dermatologist under the following circumstances:

• Acne affects the patient emotionally.
  
  
• Over-the-counter products fail to improve symptoms.
  
  
• Scars form after lesions clear.
  
  
• Nodules are present, in addition to whiteheads, blackheads, and reddened spots on the skin.
  
  
• Darker patches appear on the skin where acne lesions have cleared (in people with dark skin).

People concerned about their acne should contact a dermatologist as early as possible. Early treatment often leads to the best results and helps prevent scarring.