Causes and risk factors of melanoma

The most common cause of melanoma is too much exposure to UV radiation, which is found in natural sunlight, sunbeds or sunlamps. UV radiation can damage the DNA (genetic material) in our skin cells and cause skin cancers such as melanoma.

Other factors that may increase your risk of developing melanoma include:

  • Your skin type – having fair skin, red or fair hair, blue eyes and freckles, can make you more sensitive to the sun.
  • If you have lots of moles (over 100), or have large or irregular-shaped moles.
  • A family history of melanoma.
  • Having a low immunity.

If you are worried about your risk, speak to your GP. You can be referred to a skin specialist for an assessment of your skin.

Some exposure to sunshine is healthy, but it is important to limit the amount of time you spend in the sun. Protect yourself well from sunlight and do not use sunbeds.

Ultraviolet light exposure

The main risk factor for developing melanoma is exposure to UV (ultraviolet) radiation. This can be through natural sunlight or the artificial light used in sunbeds or sunlamps. UV radiation damages the DNA (genetic material) in our skin cells. This can cause skin cancers such as melanoma.


In the UK, the number of white people developing melanoma and other skin cancers is steadily rising. One of the reasons for this is increased sun exposure during sunny holidays. Increased public awareness has also led to a rise in the number of very early and thin melanomas being diagnosed.

It is important to be aware of the damage that too much sun exposure can cause. You should try to take steps to protect yourself. But, experts recommend regular exposure to a small amount of sunshine. This helps our bodies make vitamin D, which keeps our bones and teeth healthy. It also helps our immune system and has some anti-cancer effects.

The amount of exposure you need depends on your hair and skin type, the time of year and which part of the world you live in. It is important not to stay out in the sun for long enough to let your skin redden or burn. Severe sunburn that causes the skin to blister, especially during childhood, can increase the risk of melanoma in the future.


Sunbeds use artificial UV rays that damage the DNA in your skin. They may increase the risk of melanoma. The more you use a sunbed or lamp, and the earlier in life you begin using them, the greater your risk.

It is important not to use sunbeds, and to take precautions to protect yourself from too much sun exposure. This is especially important if you have had melanoma or any other type of skin cancer in the past. It is also important if you are at an increased risk of melanoma.

Other factors

Although exposure to UV radiation from the sun or sunbeds is one of the main risk factors for developing melanoma, it is not the only one. Like other cancers, there are many things that may lead to melanoma developing.

Your skin type

People with fair skin, who have red or blond hair, green or blue eyes and freckles, are more sensitive to the sun. Because of their skin type, they burn more easily. This means they are more at risk of getting melanoma. Having naturally darker skin lowers your risk of getting melanoma. But it does not mean that you will never get it. People from India, Asia and Africa have a lower risk of melanoma because their skin produces more melanin.

Having lots of moles and unusual moles

People who have a lot of moles, especially those with over 100 moles, have a higher risk of getting melanoma. So do people with moles that are bigger than average, or that have an irregular shape or colour. These moles are sometimes called atypical dysplastic naevi. They rarely change into melanoma, but it is important to check them regularly for changes. Having lots of moles and atypical moles can run in some families.

Your risk of melanoma is also increased if:

  • you were born with a dark, hairy mole
  • you were born with a large birth mark (over 20cm), known as a congenital naevi.

The risk from average size birth marks is very small.

If you have lots of moles or unusual moles, you can be referred to a skin specialist for advice and an assessment of your skin.

Family history of melanoma

Your risk of developing melanoma is increased if you have a close relative who has had melanoma. This may be because you have similar skin colour. But it could also be because a small number of melanomas (about 1 in 10, or 10%) are thought to be caused by genes that can run in families.

If you have a strong family history of melanoma, you may be referred to a genetic counsellor to discuss having a genetic test. The test will look for a gene called p16. This is a gene that can increase the risk of melanoma. The p16 gene may also be linked to an increased risk of pancreatic cancer. Your genetic counsellor will also discuss this with you. However, like all cancers, melanoma may be caused by a large number of genes that we cannot test for yet.

People with a very strong family history of melanoma and other types of cancer should be referred by their GP to a dermatologist and the family cancer clinic. We have more information on cancer genetics.

Reduced immunity

People with a weakened immune system have an increased risk of melanoma. This could be due to HIV or taking drugs that suppress the immune system, for example after an organ transplant.

Back to Diagnosing

How melanoma is diagnosed

Usually you’ll begin by seeing your GP, who will examine you and decide whether to refer you to a hospital specialist for further tests and treatment.