What is the cause of acne?

Exactly why some people get acne and others don’t is unknown. It is thought to be at least partly hereditary.

Other factors are:

hormonal activity, such as the menstrual cycle and puberty
stress, through increased output of hormones which can trigger more oily skin
hyperactive sebaceous glands – producing more oil
accumulation of dead skin cells
bacteria in the pores, to which the skin reacts
skin irritation or scratching, picking or squeezing spots activates inflammation
use of anabolic steroids
some medications can cause or make acne worse (for example, treatment for epilepsy)

Traditionally, attention has been focused mostly on hormone-driven over-production of sebum as the main contributing factor for acne. More recently, attention has been given to abnormal changes within the follicle which can cause acne.

Development of acne vulgaris in later years is rare, and a skin condition with a similar appearance called rosacea is often confused with it in the older age groups. True acne in older adults may point to an underlying condition such as pregnancy, polycystic ovary syndrome or the rare Cushings syndrome.

What does not cause acne

There are many misconceptions about the condition:

Diet. It has been alleged that chocolate, fried foods and sugar can cause acne but this is unsubstantiated by research. The consensus is that acne sufferers should experiment with diet as adjustments can help different people, but there is no across the board recommendations to help with acne.
Poor personal hygiene. Acne is not caused by dirt. This misconception probably stems from the fact that acne involves skin infections. In fact, the blockages that cause acne occur deep in the skin where it is impossible to wash them away. These plugs are formed by the cells and sebum produced by the body. Bacteria involved are the same bacteria that are always present on the skin. Regular washing can reduce, but not prevent acne. Anything beyond very gently cleansing can actually make it worse by damaging or over-drying the skin.
Sex. Common myths are that celibacy or masturbation cause acne, and conversely that having sex can cure it. There is no scientific evidence that any of this is true.