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.
  • Having a low immunity.
  • A family history of melanoma.

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’s important to limit the amount of time you spend in the sun. Protect yourself well from sunlight and do not use sunbeds.

Risk through UV radiation

The main risk factor for developing melanoma is exposure to UV radiation. This can be through natural sunlight, or through 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.

Sunlight

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 screening has also led to a rise in the number of very early and thin melanomas being diagnosed.

It’s important to be aware of the damage that too much sun exposure can cause, and to take steps to protect yourself. However, 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’s important not to stay out in the sun for long enough to let your skin redden or burn. Episodes of severe sunburn that cause the skin to blister, especially during childhood, can increase the risk of melanoma in the future.

Sunbeds

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’s important not to use sunbeds and to take precautions to protect yourself from too much sun exposure. This is especially important if you’ve had a melanoma (or any other type of skin cancer) in the past. It’s also important if you’re at an increased risk of melanoma.


Other factors

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


Your skin type

People with fair skin, red or fair hair, blue eyes and freckles are more sensitive to the sun. Because of their skin type, they burn more easily and so are more at risk of getting melanoma. Having naturally dark (brown or black) skin lowers your risk of getting melanoma, but it doesn’t mean that you’ll never get it.


Having lots of moles and unusual moles

People who have a lot of moles (especially over 100) 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 (sometimes called atypical dysplastic naevi), rarely change into melanoma, but it’s important to check them regularly for changes. Having lots of moles and atypical moles can run in some families.

If you were born with a dark, hairy mole, or a birth mark over 20cm (congenital naevi) this also increases your risk of melanoma.

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

This increases your risk, especially if you have two or more close relatives who’ve had melanoma. Only a small number of melanomas are thought to be caused by inherited genes. Some of these genes may also be linked to pancreatic cancer. This helps explain why some families at risk of melanoma are also at increased risk of pancreatic cancer.

People with a very strong family history of melanoma or pancreatic cancer should be referred by their GP to a 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).