What is acne?

If you have acne you may find it reassuring to know that you are not alone. Acne is one of the most common skin conditions in the world, with almost nine out of ten people having it in a milder form.

You do not have to get lots of spots for it to be called acne. Acne is simply the name that doctors give to many types of spots. Whether you prefer to call them spots, zits, breakout, pimples, blemishes, plukes or acne is simply a matter of personal choice.

This article will discuss all types of spots, from the mildest to the most severe, and the word ‘acne’ will be used to describe all of these.

What causes acne?

Acne is a common condition that begins with small blockages of oil in the hair follicles or pores of the skin. The words "Follicles" and "pores" are sometimes used interchangeably, and at other times referred to as two different things. In truth, the pore is simply the opening upon the skin of the hair follicle, which extends downward through several layers of skin.

There are four key components to the formation of acne:

• Sensitivity to hormones
• Sticky sebum
• Abnormal cell growth
• Bacteria

These four components usually work together to cause acne. However not all four components are always present, and they do not always take place in the same order.

Sensitivity to hormones

Acne can be caused by sensitivity to normal levels of male hormones (testosterone) in the body. We all have both male and female hormones present in our body, but it is testosterone that increases the level oil (sebum) production within our skin. The reason for the increased sensitivity is not clear, but it is likely to be triggered by increases in hormone production which take place at puberty. Because boys have more testosterone than girls, this explains why boys get worse acne than girls. Hormone tests are rarely necessary for people with acne because the hormone changes that affect the sebum glands are usually normal.

Sticky sebum

Sebum is another word for the grease or oil that is produced by our skin. Excess sebum is triggered by the hormone testosterone and gives the skin a shiny appearance. There may be a thin dividing line between a ‘healthy shiny glow’ and a greasy film. In individuals with acne, there is not only more sebum but it is also much thicker in consistency. This is apparent if you examine the sebum through a microscope.

This increased thickness make the sebum more ‘gloopy’ and viscous. This is a good sticky magnet for attracting anything around it. People who have acne are more likely to have larger sebaceous (oil producing) glands than those who do not have acne. This may explain the problem of excess oil production.

Abnormal cell growth

At the same time as this increase in sebum production, the skin is starting to slow down the rate at which it starts to shed dead skin cells. Although there is no good explanation for this, it is widely accepted that this is one of the factors in the development of acne.

All skin cells are produced in the bottom level of the skin (a layer called the dermis). These then grow and move gradually upwards to form the epidermis, which is the top layer of the skin. As they get closer to the top these skin cells start to die. Eventually , the top layers- the visible skin that we wash, apply make-up to, scratch, stroke or pull –die and are shed during these daily activities.

When there is abnormal cell production, not only are skin cells shed more slowly but there is a general increase in the number of cells produced, compared with normal skin. You can imagine that this combination of increased skin cell production with the reduction in the rate that these skin cells shed is a recipe for a problem.

This abnormal cell growth causes a tiny blockage of the follicle (pore). The follicle is the part of the skin that contains the hair. Attached to this follicle is the sac that produces the oil, called the sebaceous gland. The sebum (oil) produces by this gland passes up the hair follicle and is released at the top.

The blockage is described by doctors as a microcomedone, and is the starting point of acne. Now imagine that behind this blockage oil is still being produced. Because a plug has now been formed by these dead skin cells, this oil is unable to escape; it cannot just exit the follicle onto the skin as we might hope. This blockage may result in one of two things – either the oil behind the blockage becomes solid in texture and remains in the sebaceous gland doing little or this sebum starts to attract bacteria.

In the first option, where the blockage remains solid, this may show up on the skin surface in one of two ways. If the blockage of dead skin cells reaches the very top of the follicle and comes into contact with the air, it will become dark brown or black. It used to be believed that this was due to contact with oxygen leading to a chemical reaction, but more recently it has been shown that the colour change is due to the skin cells that turn our skin dark (melanin). This is the classic blackhead that most of us will be familiar with. However if the blockage occurs further down inside the follicle, just below the surface, this will produce a small raised bump in the skin. This is known as a whitehead. The whitehead often gets confused with inflammatory type acne. It has been commented that it should really be called a “skin-coloured head”. But that doesn’t have quite the same ring to it.

We have now described what is known as non-inflammatory acne. This distinction from inflammatory acne is important to emphasise, because most treatments target either one or the other and not both. Most sufferers will have a combination of both types.

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Bacteria

If the blackheads and whiteheads are non-inflammatory, what is it that causes the spot to become inflamed? In an inflamed spot the same process is occurring within the skin – the blocked pore, excess sebum etc. -as described above. However the difference is what happens to the oil (sebum) when it is sitting in the follicle, trapped with nowhere to go.

Sometimes this oil provides an ideal breeding ground for a bacteria known as Propionibacterium acnes (known as P. acnes for short). This is the bacterium most commonly found in spots. Propionibacterium acne bacteria usually live on the surface of the skin causing no problems or harm. That is until they are provided with an ideal environment to live and multiply, which is exactly what the blocked follicle represents. There is no oxygen within this area and this type of Propionibacterium acne bacteria particularly likes to grow without oxygen. When these bacteria multiply, they will spread, causing damage to and around the follicle, rupturing it and attracting white blood cells (leucocytes) whose primary job is to fight infection. The white blood cells are part of and produce an inflammatory response.

To the human eye, this will now take on the appearance of a classic acne spot-yellow (the pus which is serous fluid and white blood cells) and red–which is the inflammation (increased localised blood flow). The inflammatory spots may be tiny or fairly large, and in some types of acne may be widespread and very deep. These are known as the inflammatory lesions of acne.

In reality most people will have a mixture of both types of spots, but may be prone to having more of one than the other. Some dermatologists (skin specialists) believe that you should always use acne treatments that target the non-inflammatory type of blockages in order to halt the processes that lead to the inflamed acne spots. Aspects of treatment are covered in other articles, but it is important to know which type of spots that you have.

A study showed that 50 per cent of papules (red spots) arose from normal looking skin (although a tiny invisible microcomedone may have been present); 25 per cent came from a whitehead (closed comedone) and the remaining 25 from an open comedone (blackhead). This suggests that acne can be unpredictable.