How does the sun cause cancer?

1st March 2022

With the sun beginning to emerge, many will want to spend a bit more time in parks, gardens and at the beach to get that “healthy” glow. But did you know that this glow is radiation burn caused by exposure to ultraviolet (UV) light? While being in the sunshine supplies us with vitamin D and can improve our mood, this radiation burn also increases the risk of skin cancer.

What is skin cancer?

Skin cancer is an abnormal growth of skin cells that is divided into two main types: melanoma and non-melanoma skin cancer. Non-melanoma skin cancer grows slowly in the upper layers of the skin and rarely spreads to other parts of the body. 

The second, and more dangerous, type of skin cancer is melanoma skin cancer. Melanomas can spread to other organs in the body, and in 2020 it was estimated that over 320,000 people worldwide were diagnosed with melanoma skin cancer.

Melanoma can spread to other organs in the body. It often spreads to nearby lymph nodes first, before spreading to other vital organs. If this happens, it becomes much harder to treat. That means it is very important to look out for signs of melanoma and catch it at an early stage.

What causes skin cancer?

Over 80% of skin cancers are caused by overexposure to UV radiation. This includes UV rays from the sun, but also from sunbeds and tanning lamps. UV radiation damages DNA in your skin cells, which can accumulate over time and increase the risk of genetic mutations that cause skin cancer. The more often you get burnt, the more damage is done and the higher the risk of skin cancer. It’s also important to know that you don’t necessarily need to get a sunburn for UV rays to damage your cells.

What to do when you get sunburnt?

The best thing to do is to stay out of the sun, cover up when you have to go outside and give your skin time to heal. Drink plenty of water, use cool compresses and pain medication if necessary and see your GP if you think the burn is more severe than can be handled at home. For more advice, please see the NHS website on sunburn.

How to avoid it?

The single best thing you can do for your skin is to never get sunburnt. Getting sunburnt just once every two years can triple your risk of melanoma – the most dangerous form of skin cancer.

Using sun lotion with a high SPF, covering up with clothes, staying in the shade and avoiding the midday sun are all sensible things to do. Check out the NHS website for more tips on sun safety.

What about tanning beds?

Tanning beds also send out harmful UV rays and a single session can increase your risk of skin cancer. They are not a safe way of laying down a “base tan” and really should be avoided. The WHO puts them in the same category – carcinogenic to humans – as cigarette smoking.


You may also be at an increased risk for skin cancer if you:

  • Have had non-melanoma skin cancer before
  • Have a family history of skin cancer
  • Have pale skin that burns easily
  • Have lots of moles and freckles
  • Have red or blonde hair
  • Are taking medicine or have a medical condition that suppresses your immune system

What happens when you get sunburnt?

UV radiation

UV radiation from the sun is always present, whether it’s a cloudy day or blazing hot outside. Some types of UV radiation can even get to you through windows, which is why it’s a good idea to wear some form of SPF every day. There are three main types of UV radiation – UVA, UVB and UVC. You don’t really need to worry about UVC as it is absorbed by the Earth’s atmosphere. UVA and UVB rays are the ones that cause serious harm by penetrating into the skin and damaging proteins, membranes and the DNA in your skin cells.

A as in ageing

UVA rays – A as in ageing – penetrate deep into the skin where they cause damage to elastic fibres and DNA. They are thought to be responsible for 80% of visible skin ageing.

B as in burn

UVB rays – B as in burn – hit the top layer of your skin and cause the typical symptoms of sunburn. They damage DNA and kickstart an inflammatory response, leading to swelling, redness, heat and pain in the affected area. This immune response already begins while you’re still enjoying the warming rays from the sun and peaks about one or two days later, which is why you sometimes won’t realise how badly you got sunburnt until it’s too late. Some of the cells in your skin will also start producing melanin to protect the skin, resulting in a tan. But any form of tan means that DNA in your skin cells has been damaged, so unfortunately there is no safe amount of tanning.


How to spot skin cancer?

For melanoma skin cancer, any change to your skin can be a concern and people are advised to regularly check their entire body for new or changed moles. The commonly used guidelines include looking for the ABCDE signs:

  • Asymmetry – two halves of the mole differ in shape
  • Borders – edges may be irregular or blurred, sometimes show notches
  • Colour – may be uneven, different shades of black, brown and pink
  • Diameter – most melanomas are at least 6mm across
  • Enlargement or elevation - changes to size or how raised from the skin

The more common non-melanoma skin cancer is not connected to moles and is often less dangerous than melanoma. Nevertheless, people should look out for non-melanoma skin cancer signs:

  • Scab/sore that won’t heal
  • Scaly/crusty patch of skin that is red/inflamed
  • Flesh coloured lump that won’t go away and grows
  • Volcano like growth with rim and crater

To find out more about the symptoms and how to spot skin cancer, go to the NHS website.

Search our melanoma research

How is skin cancer diagnosed and treated?

Skin cancers are usually diagnosed by taking a biopsy (tissue sample) from the suspected area. In the case of melanoma, the doctor might also check if there has been any spread to the lymph nodes.

Treatment for both non-melanoma and melanoma skin cancer mainly consists of surgery. Surgery is usually curative for non-melanoma skin cancer and can be successful in melanoma skin cancer if found early enough. In the case of advanced melanoma skin cancer, additional treatment might be given, including drugs that target specific genetic changes.

If you suspect you might have skin cancer or have found any changes to your skin, please contact your GP as soon as possible to get it checked out.

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