Increased sebum production

The response of the body to increased circulating androgens (which generally begins to occur at 7–8 years of age) is twofold. Firstly, the androgens drive changes in both sebocytes and follicular keratinocytes which lead to microcomedone formation. Microcomedones are non-inflammatory lesions which are considered the first lesions of acne, i.e. both inflammatory and non-inflammatory acne lesions are preceded by a microcomedone (Gollnick et al., 2003). Secondly, the androgens lead to an increase in sebum production (Gollnick et al., 2003).

Sebum is made up of lipids (triglycerides, waxes, free fatty acids and squalene) and the debris of dead fat-producing cells. As a substance in itself, it is odour free; however, bacterial activity on the sebum does produce a distinctive odour known as body odour. Its purpose is to waterproof the skin and protect it from becoming dry and brittle. Sebum has the unique ability to support the growth of the bacteria P. acnes and as such acne cannot occur without the presence of sebum (Thiboutot, 2008). If the amount of sebum produced can be reduced, there is a consequent decrease in P. acnes (Leyden and McGinley, 1993). This mechanism is discussed further in the section on treatments. It seems that the highest density of P. acnes is found in areas most rich in sebaceous glands (Leyden and McGinley, 1993).