Fun in the sun ruins our skin
In New Zealand, most melanomas are related in some way to ultraviolet radiation (UVR). UVR comes from the sun or from man-made sources such as sunbeds and tanning salons. UVR on the earth's surface is composed of short wavelength UVB and long wavelength UVA rays.
- UVR damages skin cells and affects the immune system.
- There is more UVR when the sun is overhead in the middle of the day and in summer.
- There is also more UVR at high altitude or when the sun's rays are reflected from a white or shiny surface such as snow or beach sand.
- Sunbeds produce a high level of UVR.
| Sun at the beach | Reflection from snow | High altitude | Artificial UV |
|---|---|---|---|
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Ultraviolet radiation causes skin cancer
Damage from UVR begins as soon as the sun's rays reach our skin. UVR causes many visible and invisible changes in skin cells. These include:
- Sunburn
- Tanning
- Suppression of the immune system
- Moles and freckles
- Ageing changes: yellowing, wrinkled, furrowed, dry skin
- Non-melanoma skin cancer: actinic keratoses, basal cell carcinoma and squamous cell carcinoma
- Melanoma
Skin cells include keratinocytes, which produce keratin (a protein that is the building-block in skin, hair, nails and horn) and melanocytes, which produce melanin (a brown pigment). Melanin protects the skin by absorbing UVR before it can cause any damage.
| Sunburn | Actinic keratoses | Basal cell carcinoma | Squamous cell carcinoma |
|---|---|---|---|
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- See more images of actinic keratoses
- See more images of basal cell carcinoma
- See more images of squamous cell carcinoma
Genetic factors
The main cause of melanoma is the sun, but genetic factors are also important. Genes determine:
- The colour of our skin – dark skin is less likely to be damaged by UVR
- The number and type of moles – people with many moles or large, unusual moles are more likely to get melanoma
- Familial melanoma – some families are especially prone to melanoma.
Cancer can occur when genes are damaged.