What causes blemishes? and how do they develop into acne?

The causes of acne: how blemishes form
There are many, complex factors involved in the development of blackheads, whiteheads and pimples

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. You can read more about all these potential causes and triggers in the causes and triggers of 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. You can find out more about the different types of acne here.

It all 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. 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 in the skin
Tiny inflammations around the hair follicles are one of the main causes of acne.

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).*

We now know that inflammation is present at every stage of the development of acne, not just when blemishes are visible on skin’s surface.

Dr med. Markus Reinholz, Dermatologist

Micro-inflammation in the skin
Tiny inflammations around the hair follicles are one of the main causes of acne.

Then comes seborrhea and hyperkeratosis

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 blemish prone skin in general 

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.

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.
Diagram of a blackhead

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.

Blocked pores can cause blackheads and whiteheads

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 and acne in scarring. 

P.acnes bacteria causes acne to develop and spread
P.acnes bacteria decomposes sebum creating substances that cause further inflammation.

* Quelle: Recent Advances in Acne Pathogenesis: Implications for Therapy, Shinjita Das, Rachel V. Reynolds, Am J Clin Dermatol (2014) 15:479 – 488 DOI 10.1007/s40257-014-0099-z

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