There are many different types of acne. “Common” acne (acne vulgaris) can be divided into four categories according to severity:

• Type 1. Predominantly comedones (whiteheads and blackheads) with an occasional small pimple (papule or pustule). Type 1 does not involve scarring.
  
  
• Type 2. Comedones and more numerous pimples, mainly facial. Type 2 involves mild scarring.
  
  
• Type 3. Numerous comedones and pimples, spreading to the back, chest and shoulders. Type 3 involves an occasional cyst or nodule and moderate scarring.
  
  
• Type 4. Numerous large cysts and nodules on face, neck and upper trunk. Type 4 involves severe scarring.

Another common form of acne is acne rosacea (rosacea), which includes facial discoloration (reddening). Other types of less common acne may be characterized by severity and symptoms or by causes. Types of acne categorized by severity and symptoms include:

• Acne indurate. Common acne with chronic, discolored, hardened surfaces.
  
  
• Acne keratosa. Acne that occurs at the corners of the mouth where nodules crust over to form horny plugs.
  
  
• Acne ciliaris. Acne that occurs at the edges of the eyelids.
  
  
• Acne papulosa. Acne with papule formation and very little inflammation.
  
  
• Acne varioliformis. Acne with pustules occurring mostly on the temples and front of the scalp and lesser occurrence on the chest, back or nose.
  
  
• Acne atrophica. Acne with residual pitting and scarring.
  
  
• Acne pustulosa. Acne with pustule formation and subsequent deep scars.
  
  
• Acne urticaria. Acne with itching hives (small swellings on the skin).
  
  
• Acne conglobata. Acne with abscesses (pus pockets), cysts and depressions that leave scars.
  
  
• Cystic acne. Acne with cysts.
  
  
• Acne fulminans. Rare type of acne marked by inflamed, tender, crusting lesions on the upper trunk and face. Acne fulminans occurs suddenly and typically affects adolescent males. It is often accompanied by fever, high levels of white blood cells and an elevated sedimentation rate. It is occasionally accompanied by inflammation in several joints.
  
  
• Acne keloidalis nuchae. Also called keloid acne. Acne keloidalis involves infection of the hair follicles at the back of the neck. This type of acne causes scars and thickening of the skin, and almost exclusively affects African American men.

Types of acne categorized according to cause include:

• Halogen acne. Acne that occurs after exposure to halogens (e.g., bromides, iodine, chlorine).
  
  
• Chloracne. Type of halogen acne that occurs after exposure to chlorinated chemicals, such as the chlorine used to treat pool water.
  
  
• Petroleum acne. Acne that occurs in individuals who work with petroleum and oils.
  
  
• Steroid acne. Acne that results after the systemic or topical use of steroids, including corticosteroids and anabolic steroids. Often occurs predominantly on the upper back and shoulders.
  
  
• Summer acne. Also called tropical acne. Summer acne occurs in hot, humid weather or is made worse by such weather. It predominantly affects the neck, chest, back and legs, and often occurs in individuals unaccustomed to such climates.

In addition, acne occurring among newborns and infants is known as acne neonatorum.