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Melanoma risks and causes

There is one main factor that increases the risk of developing melanoma – ultraviolet light. Ultraviolet light comes from the sun or sunbeds. But some people are more at risk of getting melanoma than others. Other risk factors include

  • Moles – the more moles you have, the higher your risk
  • Being very fair skinned – especially with fair or red hair, or having lots of freckles (although people with darker skins can still get melanoma)
  • Sunburn – getting badly sunburned, particularly in childhood, increases your risk of melanoma
  • Where you were born – fair skinned people born in a hot country, such as Australia or Israel, have a higher risk of melanoma throughout their life
  • Sun exposure – on holiday, as well as sitting in the sun or sunbathing at home
  • Sunbeds – using sunbeds, particularly before the age of 35
  • Sunscreen – using sunscreens may protect you, as long as you don't spend too long in the sun

There are a couple of other known risk factors. You are more at risk of developing melanoma if a close relative has had it. Having had a melanoma or another type of skin cancer increases your risk. Having a lowered immunity also increases your risk.

 

CR PDF Icon You can view and print the quick guides for all the pages in the About melanoma section

 

 

How common melanomas are

About 13,300 people are diagnosed with melanoma in the UK each year. It is the 5th most common cancer overall in the UK, excluding non melanoma skin cancer. The number of people getting melanoma now is more than 4 times higher than it was 30 years ago. In people over 15, the incidence steadily rises with age. It is now one of the most common types of cancer in people between the ages of 15 to 34. The highest incidence is in people over 80.

Some of the increase in melanoma may be because doctors are better at watching people for signs of melanoma, and detecting it at an early stage. But doctors think that mostly, it is to do with a change in how much time we spend in the sun, such as more people taking holidays abroad.

 

Ultraviolet light

There is one main environmental factor that increases the risk of developing melanoma - ultraviolet light (radiation). Ultraviolet light comes from the sun or sunbeds. But some people are more at risk of getting melanoma than others, as this page explains.

Over exposure to sunlight can cause patches of rough, dry skin called solar keratoses. Some patches are skin coloured, other patches are pink, red or brown. Studies show that people with solar keratoses have a risk of melanoma that is 4 times higher than the general population.

 

Moles and melanoma

Some of us have more moles than others. The more moles you have on your body, the higher your risk of melanoma. Of course this doesn't mean you will definitely get melanoma if you have lots of moles. But it does mean you should be very careful about exposing yourself to the sun. And you should keep an eye on all your moles. There is information about this in the page on symptoms of melanoma.

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 one greater than 5mm in diameter. Also, people with just 1 unusually shaped or very large mole (atypical naevi) have a 60% increased risk of melanoma. The risk increases with the number of atypical naevi, and people with 5 or more have 10 times the risk of people without any atypical naevi.

 

Skin colour and freckling

People who are very fair skinned, especially with fair or red hair, are more at risk of developing melanoma. So are people with a lot of freckles. People with darker skins can still get melanoma but they have more natural protection against it. It is extremely rare for black people in the UK to get melanoma. If melanoma occurs in African or Asian people they are mostly a type that occurs on the soles of the feet or the palms of the hands (acral lentiginous melanoma). This type of melanoma can also grow under the nail. In the UK, if you are fair skinned and have a tendency to freckle in the sun, you are most at risk.

 

Sunburn

If you have a tendency to get sunburn, you are at more than average risk of melanoma. People most at risk are those who don't tan at all, such as the fairest skinned people and people who go red and then peel before getting a tan.

Research has looked into the link between sunburn and melanoma. Sunburn definitely increases the risk of melanoma. People who have had sunburn are twice as likely to get melanoma than those who have not. The risk is higher if you have had sunburn several times in your life. This increase in risk is seen with sunburn at all ages, not just in childhood. 

 

Where you were born

Fair skinned people born in a hot country, for example Australia, have an increased risk of melanoma throughout their life. Their risk is higher than people who went to live in a hot country as a teenager or people with similar skin colouring who live in cooler climates. Fair skinned people born in a hot country may have exposure to the sun as a baby and young child when the skin is most delicate. This doesn't mean you will definitely get melanoma, of course. It just means you should be aware of taking care of your skin in the sun.

 

Sun exposure now and then

In the UK, most of us are not exposed to the sun for the whole year. But over the past couple of decades, more and more of us have been going abroad for two or three weeks a year for a holiday and to get a sun tan. The number of people getting melanoma has increased in the UK since it became popular to have a tan and go abroad for holidays. This concentrated sun exposure is more of a risk for melanoma than being in the sun for part of the day throughout the year. In fact, a worldwide analysis of studies shows that people who work outdoors, and so are in the sun much of the time, are less at risk of melanoma than people who work indoors and take part in outdoor hobbies. But they may be more at risk of developing other types of skin cancer.

People with higher socioeconomic status have a higher risk of melanoma and this is probably due to well off people taking more foreign holidays. But there may be other factors involved. 

It is important to be careful during hot spells in the UK. In one study in Scotland, a third of melanoma patients had never been abroad but they had sunbathed at home.

 

Sunbeds

Sunbed companies will keep trying to tell you that their type of sunbed is safe. But they aren't. We know from research that the type of ultraviolet light used in sunbeds (UVA) can cause all types of skin cancer. Sunbeds definitely increase your risk of melanoma. In 2012, an analysis of 27 studies reported that people have an increase in risk if they have ever used a sunbed. And the risk was highest for people who had used a sunbed before the age of 35. 

A study published in 2009 found that people who have regularly used a sunbed before the age of 30 have a 75% increase in their risk of developing melanoma. Using a sunbed to get a tan before you go on holiday can also increase the risk of melanoma. There is no such thing as a safe tan. For more information, see our section on preventing melanoma.

 

Sunscreen

Doctors are unclear about how sunscreen affects your risk of melanoma. This is partly because it is difficult to design studies to look at this. Some research studies have shown that using sunscreen does not reduce the risk of getting melanoma. It may even increase the risk. This may be because people wearing sunscreen sometimes stay longer in the sun because they think they are protected. So they actually get more exposure to ultraviolet light overall.

But a study in a trial in Australia reported in 2011 that regular sunscreen use by light skinned, middle aged and older people living in sunny areas can lower the risk of developing a skin melanoma. The researchers found that when people applied sunscreen generously and regularly to sun exposed areas of the body it worked like a chemical piece of clothing to block the ultraviolet radiation from the sun.

An earlier study in 2005 in Canada showed that using sunscreen in children may help to reduce melanoma risk. The study looked at 2 groups of school children over 3 years. One group was given a supply of sunscreen and parents were advised to apply it when their child would be spending more than 30 minutes in the sun. The other group did not get the advice or sunscreen. The group using sunscreen developed fewer moles. So sunscreen may help, because having more moles is known to increase melanoma risk. Sunscreens are now also more effective than those used 10 to 20 years ago. So using sunscreens, along with limiting exposure to the sun, may protect against melanoma in the future.

But it is very important not to think that using sunscreen allows you to spend longer in the sun. You still have to be careful. Most people don't put enough sunscreen on. There is detailed information about using sunscreen in the section about preventing melanoma.

 

Family history

If you have a close relative who has had melanoma, you are more at risk yourself. This is probably partly because we tend to share the same sort of colouring and skin type as our close relatives. Even if you have darker skin colouring, you should be careful in the sun, as you still have a slight increase in the risk of developing melanoma.

Some families tend to have large numbers of moles, or moles that are unusual (doctors call them atypical).  The atypical moles tend to be an irregular shape or colour and may be larger than usual. They also have a tendency to become cancerous (malignant). But most atypical moles do not turn into cancer. People with moles like this have a higher than average risk of melanoma. The highest risk factor known for melanoma is to have a very close relative (such as a mother, father, brother or sister) with melanoma and to have more than 50 moles yourself. This is called familial atypical multiple mole melanoma syndrome (FAMMM). Some families with FAMMM are also at a higher risk of developing pancreatic cancer. 

Scientists think that around 1 in 10 cases of melanoma (10%) may be linked to inherited faulty genes. A gene called CDKN2A is known to cause FAMMM. You can read more about this in our section about inherited genes. Cancer Research UK researchers are working on finding out more about this gene, and others. For the small number of families who carry these genes, sun protection is even more important.

People who have had melanoma and have a parent who has had melanoma have a risk of getting another melanoma that is 30 times higher than the general population.

 

Previous melanoma or skin cancer

People who have had a melanoma have a risk of getting a second melanoma. Their risk is between 8  to 12 times higher than other people in the population. Studies have also shown that people who have had a non melanoma skin cancer have roughly double the risk of melanoma of the general population. People who have melanoma of the eye (ocular melanoma), which is very rare, have double the usual risk of developing a skin melanoma.

 

Other medical conditions and previous cancers

Research has looked at the link between a type of eczema called atopic dermatitis and melanoma risk. One study found that people with atopic dermatitis had an increased risk of melanoma. But other research suggests that people with this type of eczema have a lower risk of melanoma. So doctors are not clear about this. People who have asthma though have a slightly lower risk. 

Studies have shown up to a 7 times increased risk of melanoma for people with Parkinson's disease. More research is needed to understand why this is. 

Women aged 50 or over who have had chemotherapy treatment for breast cancer have an increased risk of melanoma. Men who have had breast cancer have 3 times the risk compared to men who have not had breast cancer. Melanoma risk is also slightly higher in people who have had various other cancers. These include non Hodgkin lymphoma, renal cell carcinoma, certain childhood cancers, prostate cancer, thyroid cancer and leukaemia. The increase in risk may be because the cancer types share genetic or environmental risk factors. 

In 2013, researchers carried out a meta-analysis looking at inflammatory bowel disease (crohns disease and ulcerative colitis) and melanoma risk. This means they combined the information from all of the studies and looked at the results together. They found that people with inflammatory bowel disease have an increased risk of melanoma. Treatment for these bowel conditions may include immunosuppressant drugs which we know can increase the risk of some cancers. But there was an increase in melanoma risk even when people had not taken these drugs. 

 

Hormones and melanoma

Because more women than men get melanoma, researchers have been very interested in whether hormones had a part to play. There has been a lot of research into this area, looking at

  • The role of female sex hormones
  • The pill and hormone replacement therapy (HRT)
  • Pregnancy

There is no conclusive evidence that risk of melanoma is affected by any of these factors. Some women have a natural darkening of the skin during pregnancy. This may make moles show up more clearly. But it is not true that moles are more likely to become cancerous during pregnancy. There is also no evidence that pregnant women diagnosed with melanoma do worse than non pregnant women. If you are worried about this, talk to your GP.

Some studies have shown that women who have had particular changes in their womb (endometriosis or fibroma) have a 30 to 60% increased risk of melanoma. However, other studies have not shown an increased risk so we need more research to know whether there is a link.

 

Lowered immunity

Studies have shown that people with reduced immunity are more likely to develop melanoma. People may have reduced immunity due to infection with HIV or AIDS or medicines given to suppress the immune system after an organ transplant.

 

Body weight

Some studies show an increased risk of melanoma in men who have a higher body mass index, although the same has not been shown for women. But any study looking at the risk factors for melanoma needs to take into account how much time the people have spent in the sun. It may be that women with a larger body mass index expose themselves less to the sun than smaller women. So this could be why their risk is lower. Some other studies have adjusted their results for sun exposure. They found that women with a higher body mass index do have a higher risk of melanoma.

Research has shown that taller people have a greater risk of melanoma than shorter people.

 

Chemicals at work

One study has shown a higher risk of melanoma in people working as pesticide applicators who are exposed to an insecticide called carbaryl. The risk of melanoma increased further with more than 10 days of use per year and more than 10 years of use. One study has shown an increased risk with pesticide workers exposed to the chemicals maneb, mancozeb and parathion. However, more evidence is needed to support these early findings, and to rule out whether the increased risk could be due to other factors such as sun exposure patterns.

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Updated: 14 January 2014