What is acne?

Acne, also known as acne vulgaris, is a common skin condition that causes outbreaks of pimples and cysts, mainly on the face, back, arms and chest. Acne occurs when hair follicles in your skin become blocked with oil (sebum) and dead skin cells.

Its severity can range from small whiteheads and blackheads, to pus-filled pimples, through to cysts or nodules with associated skin scarring. While anyone can get acne, it is more common during the teenage years, though some people continue to experience symptoms into their 20s. Around 8 out of 10 people aged between 12-25 will develop acne. [1]  Males are more likely to develop acne than females and it tends to run in families.

Cysts

A closed sac in or under the skin that contains fluid.

Hair follicles

A tubular opening in the epidermal layer of the skin from which a hair grows.

Nodules

A small growth or lump of tissue.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Causes

Acne is caused by excess sebum, which is the body's natural oil that keeps the skin soft and helps to remove old skin cells. Sebum is produced by small glands just under the surface of the skin (sebaceous glands). Tiny pores, each containing a hair follicle, carry sebum to the skin's surface. In acne, excess oil and dead skin cells plug hair follicles. For unclear reasons, inflammation may develop within the blocked hair follicles, causing more severe forms of acne.  

Bacteria, such as Propionibacterium acnes that is normally found on the skin, are thought to contribute to the inflammation. However, recent studies have shown that their role in causing acne is less clear. Demodex mites, which are tiny parasites that normally live on hair follicles, have more conclusively been associated with causing acne and other skin conditions, such as  rosacea, in certain individuals. 

Hormonal changes

Male sex hormones, known as androgens, cause the enlargement of sebaceous glands and increase their production of sebum. For this reason, acne is more common during the teenage years, when hormones are in a state of flux. Females also have low levels of androgens and can similarly develop acne, but it is more common in males.

Acne can also result from taking artificial hormones in the form of corticosteroid medications, anabolic steroids, testosterone or some contraceptives. Similarly, as pregnancy, menstruation and  polycystic ovary syndrome (PCOS) cause hormonal fluctuations that may trigger acne in some people.

Genetic factors

Acne is more likely if at least one parent had the condition during adolescence. However, even within the same family, the symptoms may differ in severity. Although genetics are thought to play a role, no specific gene or process for passing on acne has been identified.

Diet

There is no conclusive evidence to suggest a relationship between diet and acne. There is limited evidence that low glycaemic index diets may lower acne severity. 

Smoking

There is contradictory evidence to support the link between smoking and acne. Further research is needed to examine this association.

Myths

In the past, it was thought that acne may be caused by poor hygiene, stress, sexual activity or eating certain things, such as greasy foods or chocolate. Similarly, drinking plenty of water or exposure to sunlight was thought to help prevent acne. There is no clear evidence to support any of these myths.

Anabolic steroids

Man-made drugs that are related to the male sex hormones and may be used to treat a range of conditions. Also known as anabolic-androgenic steroids.

Corticosteroid

A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.

Genetics

Related to genes, the body's units of inheritance or origin.

Glycaemic index

The glycaemic index rates carbohydrates on the basis of their effect on blood sugar (glucose) levels. A food that is high-glycaemic increases blood sugar levels quickly, while a low-glycaemic food tends to raise blood sugar levels more slowly.

Hair follicle

A tubular opening in the epidermal layer of the skin from which a hair grows.

Menstruation

The periodic shedding of the lining of a woman's uterus. Typically occurring about every four weeks between puberty and menopause (except during pregnancy). The menstrual period varies between individuals, but typically lasts 3-5 days.

Testosterone

A hormone that plays a key role in the development of male sexual characteristics and reproduction. It is produced by both sexes, but in much larger amounts in men.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Risk factors

The following factors increase the likelihood of developing acne:

  • Age - being between 13-16 years of age;
  • Hormonal changes, particularly during the teenage years, pregnancy or menstruation;
  • Taking certain hormone-based medications, such as corticosteroids, testosterone, anabolic steroids and some contraceptives;
  • Taking certain other medications, such as phenytoin, lithium, isoniazid and iodine;
  • Exposure to oily skincare or hair products;
  • A family history of acne;
  • Frequent rubbing or friction on the skin, particularly from tight clothing, hats or helmets, and;
  • Humidity or heavy sweating.

Anabolic steroids

Man-made drugs that are related to the male sex hormones and may be used to treat a range of conditions. Also known as anabolic-androgenic steroids.

Corticosteroids

A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.

Menstruation

The periodic shedding of the lining of a woman's uterus. Typically occurring about every four weeks between puberty and menopause (except during pregnancy). The menstrual period varies between individuals, but typically lasts 3-5 days.

Testosterone

A hormone that plays a key role in the development of male sexual characteristics and reproduction. It is produced by both sexes, but in much larger amounts in men.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Types

Acne can be grouped according to the cause and symptoms as follows:

Adolescent acne

Adolescent acne is the most common type, usually occurring around puberty. It usually occurs between 13-16 years of age, but symptoms tend to be worse in males aged around 18-19 years. Adolescent acne is slightly less common in females and may flare in the week leading up to menstruation. It's also sometimes known as teenage acne.

Infantile acne

Infantile acne usually occurs in children aged six months to three years. It's more common in boys than girls, and generally affects the face. Acne is rare in older children 2-6 years of age.

Acne cosmetica

Acne cosmetica is the name used to describe acne brought on by extended use of certain skin products, such as moisturisers, foundations, face creams or heavy make-up.

Oil acne

Oil acne is usually caused by exposure to petroleum or coal tar products in the workplace. For this reason, oil acne is also sometimes referred to as occupational acne. It is most likely to appear on the legs.

Drug-induced acne

A number of hormone-based medications may cause or aggravate acne. In particular, oral corticosteroid medications, testosterone, anabolic steroids and some contraceptive medications are known to cause acne. 

Anabolic steroids

Man-made drugs that are related to the male sex hormones and may be used to treat a range of conditions. Also known as anabolic-androgenic steroids.

Corticosteroid

A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.

Menstruation

The periodic shedding of the lining of a woman's uterus. Typically occurring about every four weeks between puberty and menopause (except during pregnancy). The menstrual period varies between individuals, but typically lasts 3-5 days.

Testosterone

A hormone that plays a key role in the development of male sexual characteristics and reproduction. It is produced by both sexes, but in much larger amounts in men.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Signs and symptoms

Acne causes different types of blemishes and spots, depending on the stage and severity of the condition. It most commonly affects the face, but may also appear in areas with large numbers of oil glands (sebaceous glands), including the neck, chest, back and shoulders.

The milder form of the condition results in small whiteheads and blackheads on the skin surface (non-inflammatory acne). More severe cases are marked by inflammation within blocked hair follicles (inflammatory acne). Inflammation leads to the characteristic lumps (papules) and pus-filled pimples (pustules) of acne. If left untreated, inflammation can lead to development of cysts or nodules beneath the skin, acne scars or darkening of the skin (hyperpigmentation).

Non-inflammatory acne

Whiteheads and blackheads

Hair follicles can become blocked with dead skin cells and oil, creating a plug called a comedone. A comedone that opens at the skin's surface appears as a blackhead. The dark colour of blackheads is due to skin pigment, not dirt as is often assumed.

When the body's natural skin oil (sebum) builds up within the comedone, a lump may form under the skin. If these lumps do not open out into the skin, they are described as whiteheads.

Acne often does not progress past this mild stage of blackheads and whiteheads. In these cases, the condition is also sometimes known as non-inflammatory acne or comedonal acne.

Non-inflammatory acne includes white- and blackheads.Whiteheads and blackheads are non-inflammatory types of acne. 

Inflammatory acne

Papules

Papules are small, tender, red bumps that signal inflammation or infection of the hair follicle. They occur when sebum leaks into the deeper layers of the skin.

Pustules

Pustules are white or yellow bumps that appear when pus forms due to inflammation, which then pushes through to the skin. These pustules are the classic 'squeezable' pimples often associated with acne. Sometimes, darkened acne scars may form after pustules have healed. Although usually quite small, these scars often do not fade fully, even into adulthood.   

Cysts and nodules

Cysts are soft, fluid-filled lumps under the surface of the skin, formed by a build-up of pus within the hair follicle. Sometimes, a build-up of secretions deep within the skin can cause the whole follicle to break and collapse. The result is a hard and painful nodule deep in the skin. Cysts and nodules may occur as single blemishes, or may be widespread over the face, neck, back, chest, shoulders and scalp.

Visual appearance of acne across neck, chest back and shoulders.Visual appearance of acne. 

Cysts

A closed sac in or under the skin that contains fluid.

Hair follicles

A tubular opening in the epidermal layer of the skin from which a hair grows.

Nodules

A small growth or lump of tissue.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Diagnosis

A doctor will usually diagnose acne by looking closely at the skin on your face, chest and back and evaluating the types and severity of the blemishes and spots. Symptoms may also be assessed according to a grading scale, which can help your doctor to establish a treatment plan. Acne is often graded as follows:

  • Grade 1 (mild) - mostly whiteheads and blackheads with a few papules and pustules;
  • Grade 2 (moderate) - multiple papules and pustules, mostly on the face;
  • Grade 3 (moderately severe) - large numbers of papules and pustules with a few nodules. The back and chest are also affected, and;
  • Grade 4 (severe) - large numbers of painful pustules and nodules.

Sudden onset of acne in adult women can be a sign of a hormonal condition, such as polycystic ovary syndrome (PCOS). If this condition is suspected, your doctor may look for additional symptoms, such as irregularities in menstruation or hair growth. An ultrasound scan or blood test may also be requested.

Menstruation

The periodic shedding of the lining of a woman's uterus. Typically occurring about every four weeks between puberty and menopause (except during pregnancy). The menstrual period varies between individuals, but typically lasts 3-5 days.

Nodules

A small growth or lump of tissue.

Ultrasound

A scan that uses high-frequency soundwaves to produce images of the body’s internal structures.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Types of treatment

The aim of treatment is to clear blemishes and prevent scarring, which is a common complication. Although there is no specific cure for acne, it often improves with time. If the acne is severe, your doctor may provide a referral to see a specialist skin doctor (dermatologist).

One or more of the following treatment options may be recommended:

Self care

A number of self-care measures may be suggested to avoid or control mild acne symptoms. For example, your doctor may suggest gentle cleaning products for the face and hair that will not irritate your skin. Using cosmetics, sunscreens or hair products that are labelled as 'water-based' or 'non-comedogenic' (not pore-blocking) may also help.

Avoid picking or squeezing blemishes as this may cause scarring. Other general situations to avoid may include touching the face, leaving make-up on overnight, washing more than twice a day or letting oily hair fall across the face.

Topical medications

If you have mild acne, over-the-counter lotions may be recommended to fight bacteria, dry up oil and promote shedding of dead skin cells. These lotions are applied directly onto the skin and usually contain benzoyl peroxide or salicylic acid. In cases where symptoms are severe or do not respond to initial treatments, you doctor may prescribe a stronger topical lotion or antibiotic, such as isoretinoin gel or erythromycin.

Some medications for acne can increase the skin's sensitivity to the sun. Your doctor will be able to tell you if reduced exposure to sunlight is advised.

Oral antibiotic medications

In cases of moderate to severe acne, your doctor may prescribe oral antibiotics that have anti-inflammatory and antibacterial properties. Antibiotics are usually taken for at least 6-8 weeks in combination with topical medications. Commonly prescribed oral antibiotics for acne include doxycycline or erythromycin.

Isotretinoin

For deep nodules and cysts that cannot be cleared by other treatments, a powerful acne medication called isotretinoin may be prescribed for topical or oral use. Isotretinoin acts by reducing production of the body's natural oil (sebum). However, as isotretinoin can cause birth defects in pregnant women and other serious side effects, it is only prescribed by a dermatologist.

Hormone medications

Oral contraceptives containing a combination of ethinylestradiol and a weak male sex hormone, such as desogestrel, can improve acne in women. Hormonal medications may come with their own side effects, which your doctor can discuss with you.

Light therapies

Also known as phototherapy, these treatments involve application of ultraviolet (UV) light to reduce size and activity of sebaceous glands, which produce the sebum. For treating acne scars, short pulses of light may also be applied with a resurfacing laser to remove the outer layer of damaged skin.

Cosmetic procedures

A number of cosmetic surgery options are available to reduce the appearance of scarring caused by acne. For example, affected skin may be frozen (cryotherapy) or treated with chemicals to peel away minor scarring (chemical peel).

Dermabrasion is another cosmetic procedure that involves removing severe scarring in the top layers of skin. Additional techniques involve breaking down scar tissue with a sterile needle (subcision), or injecting collagen filler directly into scars.

Collagen

A protein that is the main component of various connective tissues.

Cysts

A closed sac in or under the skin that contains fluid.

Nodules

A small growth or lump of tissue.

Dermatologist

A doctor who specialises in the diagnosis and treatment of skin disorders and related conditions.

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Potential complications

Most cases of acne are mild and tend to clear up after the teenage years. However, severe acne can lead to complications, including:

Scarring

Any type of acne blemish can lead to scarring, but it is more likely when nodules or cysts burst and damage the surrounding skin. Picking or squeezing blemishes also increases the chances of scarring.

Scars can be narrow or wide marks, which fade from purple to a lighter colour over time. In rare cases - but more commonly in people of African descent - lumpy, itchy and painful keloid scars may develop on the back and chest.

Skin hyperpigmentation

Following the inflammatory stages of acne, hyperpigmentation may occur, meaning that the affected skin may become darker. However, this is usually seen in people with a dark skin tone.

Psychological effects

As acne can affect the appearance and lead to permanent scarring, severe or long-term symptoms may lead to psychological issues such as embarrassment, social withdrawal, low self-esteem or depression.

Cysts

A closed sac in or under the skin that contains fluid.

Nodules

A small growth or lump of tissue.

Keloid scars

An overgrowth of scar tissue at and beyond the site of an original wound. The overgrowths are elevated and firm.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Prognosis

Acne symptoms often begin to improve within the first month of treatment, but it may take six weeks or longer for the skin to clear significantly. For this reason, it's important to discuss options with your doctor before giving up or switching treatments. Additionally, while a treatment can usually clear most symptoms, some blemishes may remain or new outbreaks may appear over time.

Scarring can occur if severe acne is left untreated, which in turn may lead to low self-esteem, particularly in teenagers. In some cases, acne may also continue into adulthood. However, the prognosis for acne is generally good when treatment is started soon after symptoms appear.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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Prevention

Although acne cannot be prevented from occurring in the first place, steps can be taken to stop the symptoms from coming back. For example, your doctor may suggest ongoing use of topical medications, often at a lower dose than previously prescribed. It is quite common for treatment to continue until the late teenage years, or sometimes into adulthood.

Your doctor may also recommend continuing with light therapy or oral contraceptives to help maintain clear skin. However, antibiotic medications are not usually prescribed for extended periods, as bacteria can eventually build up resistance to these treatments.

Acne breakouts may also be prevented by maintaining good skincare habits and avoiding factors known to trigger acne.

1. Psychological effects of acne. DermNet NZ. Accessed 18 September 2014, from

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