Acne Is a common skin condition that affects most people at some point. It causes spots, oily skin and sometimes skin that's hot or painful to touch.

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

Acne is very common in teenagers and younger adults. About 80% of people aged 11 to 30 are affected by acne.
Acne is most common in girls from the ages of 14 to 17, and in boys from the ages of 16 to 19.
Most people have acne on and off for several years before their symptoms start to improve as they get older. Acne often disappears when a person is in their mid-20s.
In some cases, acne can continue into adult life. About 5% of women and 1% of men have acne over the age of 25.

Causes of acne 

Acne is most commonly linked to the changes in hormone levels during puberty, but can start at any age.
It's caused when tiny holes in the skin, known as hair follicles, become blocked.
Sebaceous glands are tiny glands found near the surface of your skin. The glands are attached to hair follicles. These are small holes in your skin that an individual hair grows out of.
Sebaceous glands lubricate the hair and the skin to stop it drying out. They do this by producing an oily substance called sebum.
In acne, the glands begin to produce too much sebum. The excess sebum mixes with dead skin cells and both substances form a plug in the follicle.
If the plugged follicle is close to the surface of the skin, it bulges outwards, creating a whitehead. The plugged follicle can also open to the skin, creating a blackhead.
Harmless bacteria living on the skin can contaminate and infect the plugged follicles. This causes papules, pustules, nodules or cysts.
Certain hormones affect the grease-producing glands next to hair follicles in the skin. They can cause them to produce larger amounts of oil (abnormal sebum).
This oil changes the activity of a skin bacterium called P. acnes. P. acnes is usually harmless, but it becomes more aggressive with the oil and causes inflammation and pus.
The hormones also thicken the inner lining of the hair follicle. This causes blockage of the pores (opening of the hair follicles). Cleaning the skin doesn't help to remove this blockage.
Other possible causes
Acne is known to run in families. If both your mother and father had acne, it's likely that you'll also have acne.
One study has found that if both your parents had acne, you're more likely to get more severe acne at an early age. It also found that if one or both of your parents had adult acne, you're more likely to get adult acne too.
Hormonal changes, such as those that occur during the menstrual cycle or pregnancy, can also lead to episodes of acne in women.
There's no evidence that diet, poor hygiene or sexual activity play a role in acne.

Acne in women
More than 80% of cases of adult acne occur in women. It's thought that many cases of adult acne are caused by the changes in hormone levels that many women have at certain times.
These times include:

 periods – some women have a flare-up of acne just before their period
 pregnancy – many women have symptoms of acne usually during the first 3 months of their pregnancy
 polycystic ovary syndrome – a common condition that can cause acne, weight gain and the formation of small cysts inside the ovary

Other triggers
Other possible triggers of an acne flare-up include:
 some cosmetic products – but, this is less common as most products are now tested, so they don't cause spots (non-comedogenic)
 certain medications – such as steroid medications, lithium (used to treat depression and bipolar disorder) and some anti-epileptic drugs (used to treat epilepsy)
 regularly wearing items that place pressure on an affected area of skin, such as a headband or backpack
 smoking – which can contribute to acne in older people

A GP can diagnose acne by looking at your skin.
This involves examining your face, chest or back. They will look for the different types of spot, such as blackheads or sore, red nodules.
How severe your acne is will determine what treatment you should have.
The severity of acne is often categorised as:
 mild – mostly whiteheads and blackheads, with a few papules and pustules
 moderate – more widespread whiteheads and blackheads, with many papules and pustules
 severe – lots of large, painful papules, pustules, nodules or cysts; you might also have some scarring

Treatment 

If you have mild acne, speak to your pharmacist. They can give you over-the-counter medicines to treat it.
If these don't control your acne, or it's making you feel very unhappy, see your GP.
You should see your GP if you have moderate or severe acne. Talk to them if you develop nodules or cysts. These need to be treated properly to avoid scarring.
Try to resist the temptation to pick or squeeze the spots, as this can lead to permanent scarring.
Treatments can take up to 3 months to work, so don't expect results overnight. Once they do start to work, the results are usually good.