Background and Manifestations of Acne
The blemishes and lesions characteristic of acne arise when hair follicles in the skin become blocked with oils and particles such as dead skin cells, bacteria, or occasionally white blood cells (Bellew 2011; Beylot 2013). Sebaceous glands attached to hair follicles secrete an oil-based substance known as sebum. Sebum normally helps moisturize skin and keep it supple. However, if too much sebum is produced, the follicle can become blocked. Testosterone, the characteristic male sex hormone, stimulates sebum production and is a major contributor to the initial formation of acne lesions (Dawson 2013; Lee, Jung 2010; Bhatia 2004). This is a primary reason why acne is more common in adolescence, when sexual maturation coincides with a spike in testosterone production, especially in males.
A clogged pore may form a “blackhead,” which is called an open comedo, or a “whitehead,” known as a closed comedo (Dawson 2013). Sometimes, bacteria called Propionibacterium acnes (P. acnes) that normally reside in the skin interact with the sebum trapped in a clogged follicle and lead to inflammation (Lee 2013; Rebello 1986; Weldon 1998). Inflamed acne lesions, which are more severe than non-inflamed lesions and are more likely to lead to scarring, can be classified as follows (Webster 2002; Mayo Clinic 2011a; Beylot 2013; Hsu 2011):
- Papules - small, raised bumps that are inflamed and may be red and tender.
- Pustules - small, inflamed, pus-filled bumps that may have a white tip.
- Nodules - solid, irregular or dome-shaped inflamed lesions beneath the skin.
- Cysts - sac-like lesions containing white blood cells, bacteria, and dead cells in a liquid or semi-liquid state.
- Cysts and nodules often appear in conjunction to form nodulocystic acne, a severe form of the condition which can be very painful and often results in severe inflammation and acne scars.