A chronic inflammatory skin condition common in adolescence, but occasionally occurring intermittently throughout life. It is characterised by skin eruptions on the face, chest and back and is more common in males than in females.

Acne most commonly develops on the:

• Face – this affects almost everyone with acne
• Back – this affects more than half of people with acne
• Chest – this affects about 15% of people with acne

There are six main types of spot caused by acne:

• Blackheads – small black or yellowish bumps that develop on the skin; they’re not filled with dirt, but are black because the inner lining of the hair follicle produces pigmentation (colouring)
• Whiteheads – have a similar appearance to blackheads, but may be firmer and won’t empty when squeezed
• Papules – small red bumps that may feel tender or sore
• Pustules – similar to papules, but have a white tip in the centre, caused by a build-up of pus
• Nodules – large hard lumps that build up beneath the surface of the skin and can be painful
• Cysts – the most severe type of spot caused by acne; they’re large pus-filled lumps that look similar to boils and carry the greatest risk of causing permanent scarring

Acne is most commonly linked to the changes in hormone levels during puberty, but can start at any age.

Certain hormones cause the grease-producing glands next to hair follicles in the skin to produce larger amounts of oil (abnormal sebum).

This abnormal sebum changes the activity of a usually harmless skin bacterium called P. acnes, which becomes more aggressive and causes inflammation and pus.

The hormones also thicken the inner lining of the hair follicle, causing blockage of the pores (opening of the hair follicles). Cleaning the skin doesn’t help to remove this blockage.