Let’s start by explaining the anatomy of the skin. The hair consists of three components:

 
• the hair follicle itself with an emerging hair shaft;  
• the sebaceous (oil) gland which opens into the hair follicle;

Four factors are involved in the development of acne:

 
1. increased production of oil stimulated by androgenic (male sex) hormones. During the teens, hormones stimulate hair growth, as well as oil secretion by the sebaceous glands. Hormonal changes can stimulate sebaceous glands to produce more sebum. Therefore, anything that raises hormone levels (for example pregnancy, stress, menstrual periods and certain medicines, such as corticosteroids) could aggravate acne. The male sex hormone testosterone, which is present in both men and women, is mainly responsible, but the female sex hormone progesterone also contributes to acne in women.     Some babies are born with acne because their mothers pass certain hormones on to them just before birth or because the stress of birth makes the baby’s body release hormones. This is rare and self-limiting.  
2. Obstruction of the opening of the follicle caused by increased production of scales (keratin);  
3. Infection by a bacterium, namely Propionibacterium acnes. The bacteria Propionibacterium acnes and staphylococcus epidermidis occur naturally in hair follicles. If there are too many bacteria, they may secrete enzymes that break down sebum, promoting inflammation in the follicle. Some people may be more sensitive to this reaction than others, making their acne more severe.  
4. rupture (breakage of the follicle leading to inflammation).

Genes and skin type may predispose a person to acne. Genetic factors may play a role.

Stress may aggravate acne, but cannot cause it. Acne may cause stress.

The stages or severity of acne are:

 
• whiteheads (clogged pores not open to the surface and medically known as closed comedones) and  
• blackheads (clogged pores open to the surface and medically known as open comedones)  
• breakage of these structures lead to the development of all other lesions - the real pimple. When whiteheads rupture the hair follicle wall, pimples are formed. Solidified sebum, dead cells from the pore and bacteria are released into the skin, creating a pimple (pustule). This stage is called inflammatory acne.  
• if pustules become infected, the infection may penetrate deep into the skin and form cysts (cystic acne)  
• the cysts may rupture and leave temporary or permanent scars