How does the sun damage our skin?
Author: Emma Craythorne
Date: May 2015
Many people regard the development of a golden tan on the body as a sign of health and beauty. Although paler skin is edging back into fashion, there’s no denying that ‘tanned’ and ‘healthy’ go hand in hand. However, a tan is not a sign of health - it is a visible sign of the body’s natural response to DNA damage caused by ultraviolet (UV) radiation. Incremental damage occurs with each exposure to UV radiation, even with doses that do not produce sunburn. This damage is cumulative with time and the magnitude of the exposures. The signs of overexposure of the skin to the sun are reflected by wrinkles, patches of pigmentation (brown spots), small visible blood vessels, scaly premalignant lesions (actinic keratosis) and with enough exposure, skin cancer.
These signs occur in a younger age in patients with fairer skin types. Despite all of this it should be remembered that sunlight does provide a lot of benefits. An outdoor lifestyle can be very healthy and many sporting and relaxation activities are performed outside. An association with longevity and lower blood pressure are all associated with sun exposure, so how do we get the best of both. How do we enjoy the benefits of the sunshine and an outdoor lifestyle yet protect ourselves from the risk of skin cancer and premature aging of the skin?
What is ultraviolet radiation?
The light that reaches our skin from sunlight is made up of visible light (the colours we see) and invisible wavelengths, divided into three types: UVA, UVB and UVC. The UVA wavelength penetrate deeper into the skin and cause damage to our collagen and superficial blood vessel; UVB light causes burning. Both UVA and UVB are responsible for the development of skin cancers and premalignant lesions. In mild countries like Britain, UV levels changes between winter and summer, in countries nearer to the equator levels are high all year round. Clouds have a small effect on UV levels but you can still get burnt on cloudy days. UV levels increase at high altitude, increasing your risk of burning. UVA can pass through glass, so a window pane will not protect you from the damaging effects of UV.
How can I prevent sun damage?
The simplest strategy is to limit your time in the sun, particularly between the hours of 11am and 1pm when 30% of the UV radiation hits the earth. A useful rule of thumb is that if your shadow is shorter than you, then the risk of sunburn is greater.
Clothing is a good UV blocker, the sun protection value of fabric is related to the hole size of the fabric mesh rather than the particular fabric type. A cotton/polyester T-shirt has a sun protection value of around 15. Hats are of great value, since they cover the head and neck which gets almost continual sun exposure, even in winter. They should have a wide brim that goes all the way around, ideally around 7.5 cm.
Artificial tanning beds “Sunbeds” emit UV rays designed to give you a tan, but in doing so will also damage your skin. Sunbed use before the age of 35 increases your risk of cancer by 75%. Therefore sunbeds are NEVER recommended for cosmetic tanning purposes and it is illegal for anyone under 18 years to use them in the UK.
Which suncream should I use?
Sun creams are made from chemicals that either absorb or block UV light. Titanium and zinc oxide are sunblocks that provide a physical barrier against UV rays; these sunscreens cause the skin to appear white in colour when they are applied to the skin as they reflect visible light also. The newer formulations of these sunscreens have miniaturised the particles and as such no longer make the skin appear white in colour. The sun protection factor (SPF) value of a sunscreen is defined as the multiplier of the time that it takes for a person to burn in the sun; it is therefore a reflection of UVB radiation. This figure was derived in a laboratory setting and in real-life situations people do not apply sunscreens in this manner. An individual applying sunscreen of SPF 50 is only likely to give a true SPF of about 2.5. For example, an individual who burns after 30 minutes of sun exposure may use an SPF50 and expect to burn after 75 minutes. Wear at least a SPF 30. Protections from UVA does not have as well a standardised approach, in the UK a 5- star system has been adopted. Sun creams displaying 4 or 5 stars offer high protection.
Individuals with fairer skin types will require a higher SPF than those with a darker skin type; they should also use SPF for more extended periods of time and not just during the summer months. Effects such as photo aging are probably the result of cumulative time spent in the sun something that can be improved by the wearing of sunscreen year round.
Enjoy the sun BUT:
- Avoid going outside when the sun is at its highest point (10am to 3pm).
- Sunbeds are NEVER recommended
- Always use a high SPF sun-cream which blocks UVA and UVB radiation - even on cloudy days and if you are skiing or taking part in winter sports.
- Cover up – close knit clothes and wide brimmed hats offer the best protection.
- Children are particularly vulnerable to sun damage.
- Babies under 6 months should NEVER be left in direct sunlight.
- Children should be protected with high SPF sun cream, clothes, hats and sun shelters.
- Buy sunglasses that block out 100% of UVA/UVB rays - look for a British Standard mark or UV 400 label.
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