What is acne?
Acne vulgaris, the most common form of acne, is a skin disease characterized by the blockage of the pilosebaceous unit (sebaceous gland + follicle), that causes the formation of pimples among other types of skin lesions. It is commonly referred to as a blocked pore because the opening of the pilosebaceous unit is occluded by a plug of dead skin cells, oil (sebum) and compounded by inflammation.
There are actually several types of skin lesions involved in acne from the comedones (‘whiteheads’ and ‘blackheads’) to a papule (solid pimple), pustule (pus filled cysts), plaque (large flat-topped lesions) and even an abscess (boil) in severe cases.
The condition typically starts in the early teen years and peaks around the late teens to resolve by early adulthood. It can sometimes not occur in the teen years, or on the other hand persists all the way to the 30s, particularly in females.
How does acne occur?
Acne appears to be a combination of several factors – hormones, excessive sebum, and bacteria – which contribute to plugging the pores of the follicles and thereby preventing the passage of sebum.
First, an increase in the androgen (male hormone) levels causes the epidermis to rapidly grow without shedding fast enough (hyperkeratosis). The excess dead skin cells may cause a follicular plug which may trap sebum. In addition, the androgens and the progestogens (one group of the female hormones) to a lesser extent causes increased sebum production as discussed below.
Sebum is the oily substance secreted by the sebaceous glands and empties into the pilosebaceous ducts. It is necessary to moisturize the hair and skin to some extent. An overproduction causes the skin to become oily (seborrhea). It further contributes to the follicular plug by causing dust from the environment to adhere to it.
Propionibacterium acnes is a type of bacteria that causes inflammation of the plugged pilosebaceous unit by secreting chemical mediators that promote inflammation.
Causes of Acne Vulgaris
Acne may exist in the absence of hormonal factors. This has highlighted the genetic component to acne development. Apart from the hormonal changes that occur with puberty, various other factors have been identified as potential causes, risk factors or aggravating conditions. This includes :
- Medication like corticosteroids, lithium and some antiepileptics.
- Cosmetics, particularly covering makeup like foundation, concealer and powder.
- Hair care products, including hair oils and pomades.
- Hormonal disorders or altered hormonal states like polycystic ovarian syndrome (PCOS) or pregnancy.
- Excessive exposure to sunlight.
Source : Acne Vulgaris. Emedicine Medscape
Location of Acne and Symptoms
Acne tends to occur in the areas with more sebaceous glands – face, back and chest. This extends to the shoulders and can occur as low down as the buttocks. In the non-inflammatory state, the excess of dead skin cells and sebum form a plug known as an open comedone (blackhead) or closed comedone (whitehead). With inflammation, this progresses to pimples, cysts or nodules. Abscesses are seen in more severe cases. The degree of scarring in acne varies and is dependent on factors such as trauma to the area.
Pictures of Acne
Picture of Acne on the Face (Source : Dermatology Atlas, Courtesy of Samuel Freire da Silva, M.D.)
Picture of Chest Acne (Source : Dermatology Atlas, Courtesy of Samuel Freire da Silva, M.D.)
Picture of Back Acne (Source : Dermatology Atlas, Courtesy of Samuel Freire da Silva, M.D.)
Article reviewed by Dr. Greg. Last updated on December 4, 2011