Risks and causes of melanoma skin cancer

Your risk of developing melanoma depends on many things. This includes lifestyle factors and some medical conditions. In the UK, too much ultraviolet radiation causes around 85 out of 100 melanomas (around 85%).

Melanoma skin cancer is the 5th most common cancer overall in the UK. The number of people diagnosed with melanoma in the UK has increased over the last few decades.

Age

The risk of melanoma increases with age. So it's more common in older people. In the UK, around 30 in 100 people diagnosed with melanoma (around 30%) are aged 75 years or over. But compared to most other cancer types, it's also quite common in younger people.

Ultraviolet (UV) light

Ultraviolet (UV) light is the main environmental factor that increases the risk of developing melanoma. It's also called ultraviolet radiation. UV light comes from the sun or sunbeds. In the UK, around 85 out of 100 melanomas (around 85%) are caused by too much UV light.

Intermittent sun exposure

Some people are exposed to strong sunlight every now and then, like when they go on holiday to a hot country. These people are more at risk of melanoma than those who are regularly exposed to sunlight, such as people who work outdoors.

In the UK, most people are not exposed to the sun for the whole year. But the number of people getting melanoma has increased considerably in the UK since it became popular to holiday abroad and get a sun tan.

It's also important to be careful during hot spells in the UK.

Sunburn

People who have had sunburn are more likely to get melanoma than those who haven’t. The risk is higher if you've had sunburn several times in your life. This increase in risk is seen with sunburn at all ages, not just in childhood.

Sunbeds

Research shows that the type of ultraviolet light used in sunbeds (UVA) can cause melanoma and non melanoma skin cancer. The International Agency for Research into Cancer (IARC) has identified sunbed use as a cause of melanoma.

People who have used a sunbed have an increased risk of melanoma. And the risk is highest for people who use a sunbed before the age of 35. Sunbed use by under 18s is banned in the UK. 

Sunscreen

It's difficult to study how using sunscreen affects the risk of melanoma. This is partly because people who use sunscreen may stay longer in the sun as they think they are protected. So they may get more exposure to UV light overall.

The best way to enjoy the sun safely and protect your skin is to use a combination of:

• shade
• clothing - including hat and sunglasses
• sunscreen 

Shade and clothing are better than sunscreen at protecting your skin. You shouldn’t use sunscreen to spend longer in the sun. But it can be useful for protecting the parts of skin not covered by clothing or shade.

Skin colour and freckling

Your skin type and colour affect your risk of developing melanoma. If you tend to burn in the sun, you're more at risk. 

People who have white skin, especially those with fair or red hair, are more at risk of developing melanoma. So are people with lots of freckles.

People with black or brown skin can still get melanoma but they have more natural protection against it.

It's rare for people with black or brown skin in the UK to get melanoma. If they do, it's most often a type of melanoma that develops on the soles of the feet or palms of the hands. This is called acral lentiginous melanoma. It can also grow under the nail.

Moles

The more moles you have on your body, the higher your risk of melanoma. One study found that melanoma risk was higher in people with 100 or more common moles, compared with people with 15 or fewer.

It doesn't mean you will definitely get melanoma if you have lots of moles. But it does mean you should be very careful in the sun. And you should regularly check your skin and moles for changes.

People who have lots of unusually shaped or large moles (atypical mole syndrome) have a higher risk of melanoma than the general population.  A large mole is bigger than 5mms across.

Birthmarks

Birthmarks are coloured marks on a baby's skin when it's born. Or they can develop in the few weeks after birth. Different types of cells make up different types of birthmark.

Most birthmarks, such as the common port wine stains and strawberry marks, carry no risk of developing into a cancer. But a very rare type, called a giant congenital melanocytic naevus, can develop into melanoma if it's larger than 20cm.

Doctors recommend that you check all birthmarks regularly for any signs of change. People who have a large congenital melanocytic naevi should have regular checks by a skin specialist (dermatologist).

Family history and genetic factors

Your risk of melanoma is higher if you have a close relative who's also had melanoma. This is probably partly because we tend to share the same colouring and skin type as our close relatives.

Your risk is highest if:

• your relative had melanoma when they were younger than 30 
• more than one first degree relative have had melanoma

Some families tend to have large numbers of moles, or moles that are unusual (atypical moles). The atypical moles tend to be an irregular shape or colour and may be larger than usual. 

Around 10 out of 100 cases of melanoma (around 10%) might be linked to an inherited gene change. A number of genes can be associated with increased risk. This includes a gene called CDKN2A. This is known to cause an inherited condition called familial atypical multiple mole melanoma syndrome (FAMMM). People with FAMMM have:

• more than 50 moles, some of which are atypical and often different sizes
• at least one close relative who has had melanoma (a close relative is a parent, brother, sister, child, aunt, uncle or grandparent)

For the small number of families who carry these genes, sun protection is even more important. Some families with FAMMM are also at a higher risk of developing pancreatic cancer. People with FAMMM have regular skin checks with a dermatologist.

Other medical conditions

Research has shown that some medical conditions increase your risk of getting melanoma. 

Inflammatory bowel disease (IBD)

Inflammatory bowel disease includes illnesses like Crohn’s disease and ulcerative colitis. The risk of melanoma skin cancer is higher in people with these diseases. 

Treatment for inflammatory bowel disease might include medicines that suppress the immune system. We know this can increase the risk of some cancers. But research shows an increased melanoma risk even when people haven’t taken these medicines.

Weakened immune system

Your immune system protects the body against illness and infection. Some people with weakened immunity are more likely to develop melanoma. Studies show this is the case for people who:

• have HIV or AIDS infection
• are taking medicines to suppress their immune system (immunosuppressants) after an organ transplant

Your GP, pharmacist or the specialist looking after you will tell you if you are taking any of these medicines.

Chemicals in the workplace

Chemicals called polychlorinated biphenyls (PCBs) are known to increase the risk of melanoma skin cancer. These are found in some old electrical equipment.

There is also research that links working as a firefighter or in the petrol refining industry to melanoma skin cancer. However, this evidence is limited.

If you work in an industry where you are exposed to harmful chemicals, there are regulations in place to protect you.

Other possible causes

Stories about potential causes of cancer are often in the media and it isn’t always clear which ideas are supported by evidence. There might be things you've heard of that we haven’t included here. This is because either there is no evidence about them or it is less clear.

Further information on melanoma skin cancer risks and causes

Cancer Research UK produce more detailed information on melanoma skin cancer risks and causes. This can be found in our cancer statistics section.