How does the sun and UV cause cancer?

  • Too much ultraviolet (UV) radiation from the sun can damage DNA in your skin cells and cause skin cancer.
  • In the UK almost 9 in 10 cases of melanoma, the most serious type of skin cancer, could be prevented by staying safe in the sun and avoiding sunbeds.
  • Getting sunburnt just once every two years can triple your risk of melanoma skin cancer, compared to never being burnt.

What is UV?

Ultraviolet radiation (UV) is a source of energy that is released naturally by the sun and artificially from sunbeds.

There are two main types of UV rays that damage our skin. Both types can cause skin cancer:

  • UVB is responsible for most sunburns.
  • UVA penetrates deep into the skin. It ages the skin but contributes much less towards sunburn.

A third type of UV ray, UVC, could be the most dangerous of all, but it is completely blocked out by the ozone layer and doesn’t reach the earth's surface.

You can’t tell whether you are at risk of burning by the temperature outside. This is because you can’t feel UV rays. People can still burn on cool or cloudy days, if the UV index is 3 or more.

In the UK, the sun’s UV rays are the strongest between 11am and 3pm from mid-March to mid-October. The UV index tells you how strong the sun’s UV rays are each day.


How can UV cause skin cancer?

Too much UV radiation from the sun or sunbeds can damage the DNA in our skin cells. DNA tells our cells how to function. If enough DNA damage builds up over time, it can cause cells to start growing out of control, which can lead to skin cancer.

Anyone can develop skin cancer, but some people can have a higher risk, including people who burn more easily.

Find out about your risk of sunburn.

It’s important to remember that skin damage doesn’t only happen on holiday or in hot, sunny places. The sun is often strong enough to cause damage in the UK, even when it’s cloudy.

Whilst we all need some sun to help us make vitamin D for healthy bones, it’s minutes rather than hours. There’s no need to sunbathe to get enough vitamin D and there is no such thing as healthy tanning. Read more about the sun and vitamin D.


Does sunburn cause cancer?

Yes. Getting sunburnt increases your cancer risk.

Sunburn is skin damage and your body’s response to try to repair it. It is a clear sign that the DNA in your skin cells has been damaged by too much UV radiation.

Getting sunburn just once every two years can triple your risk of melanoma skin cancer, compared to never being burnt.



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Did you know the signs of sunburn can depend on your skin tone?

Sunburn doesn’t have to be raw, peeling or blistering. If your skin has gone pink or red in the sun, it’s sunburnt. For people with darker skin, it may just feel irritated, tender or itchy.


What should I do if I get sunburnt?

If you notice signs of sunburn, you should come out of the sun and cover up to help stop any more damage from happening. Putting on more sunscreen won’t help and won’t let you safely stay out in the sun for longer.

‘After sun’ lotion can help sunburnt skin feel better, but it can’t repair any DNA damage.

Getting sunburnt once doesn’t mean you will definitely get skin cancer. But the more times you get sunburnt the higher your risk of melanoma skin cancer. Reduce your risk of sunburn and protect your skin by using a combination of shade, clothing and sunscreen.

Find out the best ways to enjoy the sun safely.


Can skin cancer spread?

Yes. Melanoma skin cancer can grow down through the layers of the skin and spread to other parts of the body.

Remember, when skin cancer is found at an early stage, treatment is more likely to be successful. If you have noticed any unusual changes to your skin, including a mark or mole that’s new, has changed or been there for a while, speak to your doctor. Read more about melanoma skin cancer symptoms.


International Agency for Research on Cancer. Radiation. Vol 100 (2012)

Brown, K. F. et al. The fraction of cancer attributable to known risk factors in England, Wales, Scotland, Northern Ireland, and the UK overall in 2015. Br. J. Cancer. 118, 1130-1141 (2018)

Dennis, L. K. et al. Sunburns and risk of cutaneous melanoma, does age matter: a comprehensive meta-analysis. Ann Epidemiol. 18, 614-627 (2008). doi:10.1016/j.annepidem.2008.04.006.Sunburns.

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