What causes and triggers acne?

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How to prevent blemishes from forming

There are several myths around what causes acne, many of which are untrue. But all doctors agree that acne is a hormonal disease and you can find out more about the relationship between hormones and acne in our article hormones and acne. 

We also know that some of us are more genetically prone to blemishes than others and that certain medications, smoking, stress and inappropriate skincare can all trigger acne. There’s also evidence of a correlation between diet and acne.

This article focuses on the physiological causes of acne - it look at what is actually going on in our skin. We examine the multiple, complex factors involved in the development of blackheads, whiteheads and pimples and how they progress into acne.

Learn about the external factors that can cause, trigger and exacerbate acne and what you can do to help reduce their potential impact.

Acne begins with invisible micro-comedones in the skin

A comedo is a clogged hair follicle. A micro-comedone is the name given to a microscopically small, subclinical (not yet visible) comedone. These comedones, or more commonly known as clogged pores, can be prevented and treated so you can stop acne before it begins.

Micro-comedones develop as the number of keratin-forming cells in the skin multiply. This process occurs naturally, without problems, in healthy skin as the micro-comedones dissolve. But, for those with acne, the dissolving process is accompanied by inflammatory reactions known as micro-inflammations.

Micro-inflammation – root cause of acne cycle

Acne is primarily an inflammatory disease. According to the latest research, micro-inflammation is one of the main causes of acne. It is thought to be the result of the body’s immune system reacting to bacteria, lipids and or androgens (male sex hormones).1


Dr med. Markus Reinholz, Dermatologist

Seborrhea and hyperkeratosis cause blackheads, whiteheads and pimples

Internal factors such as hormonal changes (e.g. during puberty or the monthly cycle) and medication, and external factors such as environmental influences, can lead to an increase in the production of both sebum (known as seborrhea) and corneocytes (known as hyperkeratosis) which causes blackheads, whiteheads and pimples. Both these factors also play a role in the growth of bacteria, which ultimately leads to the papules and pustules associated with acne. You can read more about the terms used to describe acne, such as papules and pustules, and what they mean in our selection of articles on blemish-prone skin.

The sebaceous glands secrete an oily substance called sebum that keeps skin and hair supple. People with blemish-prone skin and acne tend to have higher levels of androgens (male hormones) in their blood. Their sebaceous glands may also be more sensitive to androgens. These androgens promote sebaceous gland growth and excess sebum production. This excess sebum production is known as seborrhea. 

Excess sebum on skin’s surface interferes with the natural process by which skin sheds dead cells (known as desquamation). The composition of the sebum lipids which build up in the sebaceous glands also trigger inflammation.

Hyperkeratosis is an abnormal thickening of the external layers of skin. It is caused by the excessive production of skin cells (also known as corneocytes) in the ducts of the sebaceous glands and by the inadequate desquamation (shedding) of dead cells as the excess sebum binds them to skin’s surface. These cells form plugs that block the sebaceous glands. 

Propinionbacterium acnes (or P. acnes), a bacteria that normally lives harmlessly on skin’s surface, also plays a role in Hyperkeratosis. It creates a biofilm (thin layer) on skin’s surface which disrupts the normal process of desquamation and contributes to the development of the plugs.

How blackheads, whiteheads and pimples develop

Sebum build up in the blocked sebaceous glands and the follicle wall bulges causing comedones (blackheads and whiteheads) and pimples:

An inflamed (raised and coloured) blemish that fills with pus and is usually painful. Pimple is the collective term often used to describe all blemishes: comedones, papules and pustules.

Open comedones (blackheads) 

A small, dark, flat spot in the skin. The dark colouration is caused by sebum reacting with oxygen and has nothing to do with dirt.

Closed comedones (whiteheads)
A raised, round blemish with a milky-white cover and a type of pimple.

Bacterial growth exacerbates visible inflammation, leading to acne

The build-up of sebum secreted by the sebaceous glands represents an ideal breeding ground for bacteria, particularly P.acnes. It starts to colonise the duct of the plugged sebaceous gland and causes the sebum to decompose. This decomposition produces substances which cause further inflammation and lead to the papules and pustules associated with acne.

In severe cases the follicular wall bursts in the late stages of inflammation. Lipids, fatty acids, corneocytes (cells), bacteria and cell fragments are released and can cause further inflammation to the surrounding skin.

You can find out more about the different forms that acne takes in the different types of acne and you can read about some of the ways that it can affect your skin in acne and hyperpigmentation.

What causes/triggers acne and makes it worse?

Person holding an ice cream
Dairy products and sugary foods may exacerbate acne

Sadly, there is no such thing as a ‘cure’ for acne, but understanding the potential triggers that can both cause and exacerbate blemishes may help you to alleviate symptoms and improve your skin condition. Here are some of the most common ones:


While research into the influence of diet on acne is both inconclusive and controversial, most scientists agree that a high Glycemic Index and dairy products may exacerbate blemish-prone skin. There is also considerable debate around the possible influence of other foods.

You can find out more about the debate around nutrition and about why some foods are thought to trigger acne in acne and diet.


Woman smoking
Smoking damages both your lungs and your skin

Research indicates that smoking exacerbates acne by causing oxidative stress to skin and altering sebum composition. 

A study carried out on 1,000 women also revealed that the proportion of acne sufferers was significantly higher among smokers (approx. 40 %) than among non-smokers (approx. 10 %)1. 

1- Capitanio et al from British Journal of Dermatology 2007 157, pp1040–1085


Person about to swallow acne medication
Certain medications can cause blackheads, whiteheads and pimples

Medications such as antidepressants, antiepileptics and steroids are known to promote acne. Prolonged use of antibiotics can also damage the flora in the gut and impact on skin health. 

Excessive use of androgens can also promote the development of acne -  Acne Fulminans, a rare condition, is a side effect of the use and abuse of anabolic steroids by some bodybuilders. You can read more about it in acne and exercise.

Inappropriate skincare

Woman applying heavy make-up
Be sure to choose non-comedogenic make-up that does not promote acne

Regular and thorough cleansing is an important step in caring for blemish-prone skin but harsh, soap-based cleansers and water that is too hot can disrupt skin’s natural balance and exacerbate symptoms. 

Some skincare products and make-up are also greasy and comedogenic (meaning they cause clogged pores and acne).


Woman feeling stressed while looking at laptop
Living with acne can be stressful, and stress does nothing to improve skin health

Some researchers believe that stress can cause our body to produce more insulin, which stimulates androgens (male hormones) that, in turn, stimulate excess sebum production (seborrhea) and hyperkeritanisation (the over production of cells that leads to blocked sebaceous glands). Find out more in acne and stress.

The speed at which wounds heal is also reduced significantly when a person is under stress2.

Long-term anxiety in particular does the skin no good and can allow acne to `flourish’. Living with acne can also be difficult and can impact on someone’s self-confidence causing further stress which, in turn, exacerbates their skin. You can find out more in the psychological impact of acne and acne and stress.

2 - Marucha PT, Kiecolt- Glaser JK, Favagehi M. Mucosal wound healing is impaired by examination stress. Psychosom. Med. 1998;60:362-5


Woman shielding her face from the sun by wearing a hat
UV radiation can make acne worse and cause pigmentation issues

Prolonged pressure and friction on skin can exacerbate acne. Friction acne - known as Acne Mechanica - is caused when tight clothing or straps (e.g. bras, wetsuits and the chin straps on helmets) hold sweat against the skin. The irritation caused by this sweat increases sebum production and leads to the development of blemishes.

You can read more about Acne Mechanica in acne and exercise. Skin irritation can also cause itching and if you scratch a lot, or keep touching the area, you will help spread bacteria and exacerbate your acne.

What can I do to help prevent acne?

Our skin is as individual as we are, so what works for one, may not work for another, but here are some steps you can take that might help your skin condition:

Nutritional science and common sense tell us that a healthy, balanced diet is the key to a healthy body and healthy skin, so try to enjoy a varied diet and keep a personal record (some dermatologists call this a 'skin diary') of anything you eat that you think may trigger blemishes and acne in your skin. If this doesn’t help them you may want to try an 'elimination diet'. The best way to do this is to eliminate the possible culprits (such as high G.I. and sugary foods and dairy products). Learn more in acne and diet.

Give up smoking. If you can’t try, at least, to reduce your nicotine consumption.

If you think the medication you are taking is exacerbating your acne, consult your doctor. They may well be able to recommend an alternative.

Cleanse skin in the morning and evening be sure to remove all make-up before you go to bed in at night.

Choose cleansers, moisturisers and treatment products that have been specially formulated for blemish-prone skin and acne. Use only products that are proven non-comedogenic (i.e. that do not cause acne) and, if you undergoing medical acne treatment, make sure you use products that are compatible with your therapy. 

The Eucerin DermoPurifyer Oil Control range is proven to reduce blemishes, soothe irritation and prevent new blemishes from appearing and includes products that work alongside medical acne treatments. Find out more in the ideal skincare products and routine for blemish-prone skin.

Try and find a way to unwind. Exercise will help you to keep your body in good shape (and feel more in control too). You can find some tips for reducing stress here.

The best steps you can take to avoid friction acne are a) to take a shower as soon as possible after sport and b) to wear cotton rather than Lycra clothing whenever possible. Try also to keep your hands away from your face and clean your mobile phone, pillow cases and towels regularly to keep bacteria to a minimum. 


Enjoy the sunshine in moderation. Avoid peak hours, and protect your skin with an appropriate product such as Eucerin Oil Control Sun Gel-Cream Dry Touch SPF50+.

Only by continually trying things out over a matter of weeks can you find out which of the various influencing factors are specifically relevant to you and can improve your skin condition. But, if symptoms persist and are bothering you, don’t forget that there‘s a wide range of medical options available to help. Consult your doctor for advice on the best treatment options for your skin. 

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