Ultraviolet light (UVA and UVB) from the sun is the main cause of most skin cancers.

Skin cancer is becoming more common and there are several possible reasons for this. People are living longer (and so their lifetime sun exposure is greater). They often have more time and money for outdoor recreation and holidays in sunny climates, and many people still consider suntans to be healthy and attractive.

People who work outdoors for a living, such as farm workers, builders and gardeners, are at an increased risk of developing skin cancer because of prolonged exposure to the sun.

It is likely that most skin damage from ultraviolet radiation occurs before the age of 20. It is thought that a build-up of overexposure to the sun over a period of several years can lead to the development of basal cell and squamous cell skin cancers.

Black- or brown-skinned people have a very low risk of developing skin cancer because the melanin pigment in their skin gives them protection. A fair-skinned person who tends to go red or freckle in the sun will be most at risk. Children and young adults who have been overexposed to the sun have an increased risk of developing some form of skin cancer. This will not show up until later on in life - usually after about the age of 40, and often not until their 60s or 70s.

The regular use of sunlamps and sunbeds increases the risk of developing skin cancer.

Areas of skin that have been badly burned, or have long-term inflammation, have an increased risk of squamous cell carcinoma.

Radiotherapy given to treat other conditions can sometimes cause skin cancers in the treatment area later in life.

People who have to take drugs which lower their immunity (immunosuppressants) - for example, after a kidney transplant - are at increased risk of getting skin cancer. However, the reason for taking the immunosuppressants outweighs the potential risk of skin cancer.

Another rare possible cause for non-melanoma skin cancer is overexposure to certain chemicals at work, including:

• coal tar
• soot
• pitch
• asphalt
• creosotes
• paraffin waxes
• petroleum derivatives
• hair dyes
• cutting oils
• arsenic.

You should wear protective clothing if you are handling these substances frequently.

Most skin cancers are not caused by an inherited faulty gene that can be passed on to other family members, so members of your family are not likely to have an increased risk of developing it. However, families are likely to have the same skin type, which may increase their risk of developing a skin cancer.

People with certain rare hereditary conditions, such as Gorlin syndrome or xeroderma pigmentosum (XP), have a higher risk of developing skin cancer.