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
Types of spots
There are 6 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 – look similar to blackheads, but may be firmer and won't empty when squeezed
- papules – small red bumps that may feel tender or sore pustules – like 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 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.
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.
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.
Teenage acne is believed to start due to an increase in testosterone.
Testosterone is a hormone that occurs during puberty. It's important for the development of the penis and testicles in boys.
It is also important for muscle and bone strength in girls.
The sebaceous glands are particularly sensitive to hormones.
A rise in levels of testosterone is believed to cause the glands to produce much more sebum than the skin needs.
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 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
Despite being one of the most widespread skin conditions, acne is also one of the most poorly understood. There are many myths and misconceptions about it:
Acne is not caused by a poor diet
So far, research hasn't found any foods that cause acne. Eating a healthy, balanced diet is recommended. This is because it's good for your heart and your health in general.
Acne is not caused by having dirty skin and poor hygiene
Most of the biological reactions that trigger acne occur beneath the skin, not on the surface. The cleanliness of your skin has no effect on your acne. Washing your face more than twice a day could just aggravate your skin.
Squeezing blackheads, whiteheads and spots is not the best way to get rid of acne
This could actually make symptoms worse and may leave you with scarring.
Sexual activity has no influence on acne
Having sex or masturbating won't make acne any better or worse.
Sunbathing, sunbeds and sunlamps don't help to improve the symptoms of acne
There's no evidence that exposure to sunlight or using sunbeds or sunlamps can improve acne. Many medications used to treat acne can make your skin more sensitive to light. Exposure could cause painful damage to your skin, and also increase your risk of skin cancer.
Acne is not infectious
You can't pass acne on to other 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
When to seek medical advice
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.
Acne and hormonal imbalance in women
If acne starts in adult women, it can be a sign of a hormonal imbalance, especially if it's accompanied by other symptoms such as:
- excessive body hair (hirsutism)
- irregular or light periods
The most common cause of hormonal imbalances in women is polycystic ovary syndrome (PCOS).
PCOS can be diagnosed using a combination of ultrasound scans and blood tests.