What is acne?

Acne is a hormonally driven condition which affects the pilosebaceous gland. Sebaceous glands are found on most parts of the human body except for the palms of the hands and the soles and dorsum of the feet. They are found predominantly on the face and scalp, but also exist in relatively large numbers on the chest and back. This explains the tendency for acne to appear in these areas. There is considerable variability in the size of the glands both between individuals and on different anatomical sites on any single individual. Acne lesions and severity assessment have been introduced in Assessment and planning care.

The sebaceous glands respond to circulating androgens by producing sebum. In acne, sebum production is increased either because the sebaceous gland becomes overly sensitive to circulating androgens or because the levels of circulating androgens are particularly high (O’Connell and Westhoff, 2008). Testosterone is the primary androgen associated with acne. It is produced in the adrenal glands, the ovaries in women and testes in men. Whilst generally thought of as a male hormone, testosterone is present in both males and females and becomes an important factor at puberty when the reproductive organs become active.

There are four key processes which occur to produce acne lesions.

1. Increased production of sebum;
2. Hyperkeratinisation within the hair follicle leading to follicular plugging;
3. Increased bacterial activity within the follicle as there is enhanced colonisation with Propionibacterium acnes;
4. Release of inflammatory mediators (e.g. cytokines, tumour necrosis factor) into the follicle and surrounding dermis causing increased inflammation (Figure 10.1).

Each of these four processes will now be considered in turn.

Figure 10.1 Acne pathogenesis. (Source: Reprinted from Graham-Brown and Burns, 2006.)