A comedone is a small black or white coloured spot which often occur as part of an acne outbreak and develops on the face, neck, chest and back. This is one of several physical changes that occur during puberty which affects boys more than girls.

They occur due to an over-production of oil within the skin called sebum which gives the skin a silky smooth appearance. But if excess amounts of this oil are produced during puberty or from other causes then it leads to a rash of spots or comedones.

A comedone is basically a blockage in a skin pore which swells and forms a tiny bump. This is repeated several times to create a rash of spots with a rough, grainy texture.

Are comedones and acne the same?

Not necessarily. Comedones are one type of spot which develops during acne but they can also occur for other reasons. It is possible to develop comedones but not have acne.

But comedones are a very common feature of acne.

How does acne develop?

The answer is simple. Sebum. Sebum is produced by the sebaceous glands within the skin which helps lubricate the hair follicles and the skin. But rising hormone levels during puberty over-stimulate the sebaceous glands, causing an excess production of sebum.

This sebum builds up underneath the skin. It attracts the attention of bacteria in the skin which attack and thrive within this oily environment. This causes a localised inflammation and the formation of spots or acne. These spots take the form of comedones, pustules, nodules and cysts.

Two types of comedones

There are two types of comedones:

Open comedones

An open comedone is wide open to the skin and develops when excess sebum overflows through the pores and onto the surface of the skin. The sebum combines with naturally occurring bacteria and dead skin cells and multiplies, leading to an outbreak of spots or acne.

The open spot or comedone allows air to access its centre, oxidising the sebum within which changes from white to a dark colour. This is known as a blackhead.

Closed comedones

These develop in the same way as an open comedone. But they have blocked openings instead which prevents oxygen from reaching the centre of the spots and changing their colour.

Closed comedones remain the same colour and are known as ‘whiteheads’.

If an acne outbreak occurs near to the surface of the skin then it will result in comedones and other similar types of spots such as pustules. But deep seated inflammations lead to the formation of nodules and cysts which are painful and liable to cause scarring.

Diagnosing comedones

If you are in your teens and notice an outbreak of these spots on your skin then they are more than likely to be acne. This is particularly the case if you are a teenage boy as boys are at greater risk of acne than teenage girls.

Acne and/or comedones can be treated at home using over the counter medications such as acne creams or lotions. This is suitable for mild versions but severe cases will need medical attention.

Visit your GP if you are suffering from a severe case of acne or comedones. He or she will prescribe a stronger cream or lotion or will refer you to a dermatologist for further investigation.

Treatment for comedones

There are various types of treatment available which are done under medical supervision. These include topical creams which are applied to the affected areas of skin, steroids, antibiotics or photodynamic therapy.

Find out more about these and other treatments in our dermatology treatments section.