Different Types of Acne

1
Normal Pore

How does acne form? All acne is a disorder of the pilosebaceous unit, which is made of a hair follicle, sebaceous glands, and a hair. These units are found everywhere on the body except on the palms of the hands, the soles of the feet, the top of the feet, and the lower lip. The number of pilosebaceous units is greatest on the face, upper neck, and chest.

Sebaceous glands produce a substance called sebum, which is responsible for keeping the skin and hair moisturized. During adolescence, sebaceous glands enlarge and produce more sebum under the influence of hormones called androgens. After about age 20, sebum production begins to decrease.

Sebum produced by the sebaceous gland combines with cells being sloughed off within the hair follicle and fills up the hair follicle. When the follicle is full, the sebum spreads over the skin surface, giving it an oily appearance. When this process works correctly, the skin is moisturized and remains healthy. When this process does not work correctly, the skin can become either overly dry or overly oily, the latter of which raises the risk for acne.​

This series of illustrations shows how different types of acne develop and how to treat each specific kind. This first illustration depicts a normal pore so you can compare the other pictures of acne against it. 

2
Microcomedone (Early Acne)

Several factors contribute to the start of an acne lesion:

  • Corneocytes, or skin cells, become more sticky as they are shed and accumulate in the pore instead of flowing out onto the skin.
  • More skin cells are shed at the top of the pore than the bottom.
  • Sebum production is increased.

During this stage, the pore looks normal on the outside, but there are distinct changes in the cells surrounding the pore. As the material in the pore builds up, it creates a bottleneck that prevents sloughing. The medical term for this stage is a microcomedone.

The bacterium Propionibacterium acnes, often shortened to P. acnes, normally resides in the pores. It uses sebum as a nutrient for growth. As sebum production increases, the number of P. acnes bacteria increases in the pore. In the microcomedone stage, the bacteria do not cause infection because they are in only the material inside the pore, not infecting the skin.

These are some medications that may help at this stage.

  • Over-the-counter benzoyl peroxide kills bacteria and helps prevent P. acnes from overgrowing.
  • Prescription tretinoin products like Retin-A, Retin-A Micro, and Avita reverse the stickiness of the skin cells, allowing them to slough normally.
  • Over-the-counter salicylic acid 2% lotion is a beta hydroxy acid that also reverses the stickiness of the skin cells.

3
Whitehead or Closed Comedone

As the sebum from the sebaceous gland and sloughed skin cells, also known as corneocytes, build up, they become compacted and thick. If the opening of the pore is narrow or closed, this becomes a closed comedone, also known as a whitehead (because the lesion is raised and white in appearance).

As sebaceous material builds up, inflammation develops in the cells surrounding the pore. Whiteheads can be infected or not infected, depending on whether the P. acnes bacteria have been able to infect the cells around the pore.

These are some medications that may help at this stage.

  • Over-the-counter benzoyl peroxide kills bacteria and helps prevent P. acnes from overgrowing.
  • Prescription tretinoin products like Retin-A, Retin-A Micro, and Avita reverse the stickiness of the skin cells allowing them to slough normally.
  • Over-the-counter salicylic acid 2% lotion is a beta hydroxy acid that also reverses the stickiness of the skin cells.
  • Prescription topical antibiotics kill the P. acnes bacteria and might be used if some of the whiteheads are infected.
  • Prescription oral antibiotics also kill the P. acnes bacteria and might be used if many whiteheads are infected or if there are infected papules or pustules.

4
Blackhead or Open Comedone

As the sebum from the sebaceous gland and sloughed skin cells, also known as corneocytes, build up, they become compacted and thick. If the opening of the pore is stays open, this becomes an open comedone, also known as a blackhead (because the pore looks black).

As sebaceous material builds up, inflammation develops in the cells surrounding the pore. Blackheads can be infected or not infected, depending on whether the P. acnes bacteria have been able to infect the cells around the pore.

These are some medications that may help at this stage.

  • Over-the-counter benzoyl peroxide kills bacteria and helps prevent P. acnes from overgrowing.
  • Prescription tretinoin products like Retin-A, Retin-A Micro, and Avita reverse the stickiness of the skin cells allowing them to slough normally.
  • Over-the-counter salicylic acid 2% lotion is a beta hydroxy acid that also reverses the stickiness of the skin cells.
  • Prescription topical antibiotics kill the P. acnes bacteria and might be used if some of the blackheads are infected.
  • Prescription oral antibiotics also kill the P. acnes bacteria and might be used if many blackheads are infected or if there are infected papules or pustules.

5
Pimple or Inflammatory Papule

As the sebum from the sebaceous gland and sloughed skin cells, also known as corneocytes, build up, they put pressure on the cells surrounding the pore. If enough pressure is exerted, the sides of the pore rupture and the sebaceous material leaks into the surrounding skin. Since the sebaceous material contains a lot of P. acnes bacteria, the surrounding skin gets infected and creates a red bump (what you would call a typical pimple). The medical term for this red bump is an inflammatory papule.

These are some medications that may help at this stage.

  • Over-the-counter benzoyl peroxide kills bacteria and helps prevent P. acnes from overgrowing.
  • Prescription tretinoin products like Retin-A, Retin-A Micro, and Avita reverse the stickiness of the skin cells allowing them to slough normally.
  • Over-the-counter salicylic acid 2% lotion is a beta hydroxy acid that also reverses the stickiness of the skin cells.
  • Prescription topical antibiotics kill the P. acnes bacteria and are often used if a person has some inflammatory papules.
  • Prescription oral antibiotics also kill the P. acnes bacteria and are often used if a person has a lot of inflammatory papules.

6
Pustule

A pustule is different from a pimple only because it contains white blood cells. As the immune system fights off the P. acnes infection, sometimes white blood cells (which are part of the immune system) pile up, creating pus in the pore. This is called a pustule. We know which parts of the immune system are involved in making pimples and pustules, but it is unclear why some lesions develop pus in them and others don't. This only matters from a scientific standpoint because, practically, pimples and pustules are treated the same way.

These are some medications that may help at this stage.

  • Over-the-counter benzoyl peroxide kills bacteria and helps prevent P. acnes from overgrowing.
  • Prescription tretinoin products like Retin-A, Retin-A Micro, and Avita reverse the stickiness of the skin cells allowing them to slough normally.
  • Over-the-counter salicylic acid 2% lotion is a beta hydroxy acid that also reverses the stickiness of the skin cells.
  • Prescription topical antibiotics kill the P. acnes bacteria and are often used if a person has some pustules.
  • Prescription oral antibiotics also kill the P. acnes bacteria and are often used if a person has a lot of pustules.

7
Cyst or Nodule

At times when the sebaceous material and bacteria leak into the surrounding skin, the infection spreads wider and deeper, causing scarring and the formation of nodules or cysts. These are the deep "pizza face" acne lesions that are very painful and resistant to over-the-counter treatments.

These are some medications that may help at this stage.

  • Prescription tretinoin products like Retin-A, Retin-A Micro, and Avita reverse the stickiness of the skin cells allowing them to slough normally.
  • Prescription oral antibiotics also kill the P. acnes bacteria and are often used to calm down the infection with cystic acne.
  • Isotretinoin (Accutane) may be prescribed to treat moderate to severe cystic acne. This drug does have serious side effects and needs to be monitored closely if it is used.

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