Melanoma risks and causes

In the UK each year, about 12,800 people are diagnosed with melanoma. More women than men get melanoma in the UK. 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.

There is one main 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 hard, dry, discoloured skin called solar keratosis. Studies show that people with solar keratosis have a risk of melanoma that is 4 times higher than the general population.

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 abnormal moles (dysplastic naevus syndrome) have a higher risk of melanoma than the general population. 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.

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 occur on the feet (acral lentiginous melanoma). In the UK, if you are fair skinned and have a tendency to freckle in the sun, you are most at risk.

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 with melanoma are twice as likely as other people to have been badly sunburned at least once in their lives. The risk is higher if you have had sunburn several times in your life. Sunburn in childhood is even more damaging than sunburn as an adult.

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.

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 good tan. The number of people getting melanoma has shot up 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. 

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.

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 2007, an analysis of 23 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.

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.

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). This used to be called familial dysplastic naevus syndrome, but this term isn't used much any more. The atypical moles tend to be an irregular shape or colour. They also have a tendency to become cancerous (malignant). 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 (mother, father, brother or sister) with melanoma and to have abnormal looking moles yourself.

Scientists think that around 1 in 10 cases of melanoma (10%) may be linked to inherited faulty genes. Some of these genes have been identified and Cancer Research UK researchers are working on finding out more about them. 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.

People who have had a melanoma have a risk of getting a second melanoma that is 9 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.

A large study has shown that people with a type of eczema called atopic dermatitis have an increased risk of melanoma. 

Studies have shown up to a 7 times increased risk of melanoma for people with Parkinson’s disease.

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.

People who have asthma though have a slightly lower risk. 

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 recent studies showed 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.

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.

Some studies show an increased risk of melanoma in men with a higher body mass index, although the same has not been shown for women.

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.