May 7, 2007 With the northern hemisphere summer approaching, many people will be taking advantage of the hot weather to sunbathe and relax in the hot weather in parks and on beaches.
But avoiding direct sunlight and wearing clothes which stop harmful UV rays from reaching the skin, rather than sunscreen, are the best ways of avoiding skin cancer and the aging effects of the sun. Dr Stephan Lautenschlager, Outpatient Clinic of Dermatology, Triemli Hospital, Zurich, Switzerland, and colleagues carried out the comprehensive review on sun protection strategies around the world.
The authors say: “Wearing sun protective clothes and a hat and reducing sun exposure to a minimum – should be preferred to sunscreens. Often this solution is deemed to be unacceptable in our global, outdoor society, and sunscreens could become the predominant mode of sun protection for various societal reasons, for example healthiness of a tan, relaxation in the sun.”
They add: “Nevertheless, sunscreens should not be abused in an attempt to increase time in the sun to a maximum.”
The Review highlights the characteristics of clothing that can make all the difference in terms of sun protection factor (SPF). Tightly woven, thick garments made of denim, wool or polyester offer the best protection, while cotton, linen and acetate are much less effective. Lax, dry material, and clothes that have shrunk after washing (thereby making them denser) are better at stopping harmful UV rays reaching the skin, while wet or stretched materials, and those that have been bleached, are not so good.
Sunscreen of varying SPFs is applied, depending on skin type and personal preference - but what does SPF actually mean? SPF is defined as the minimum sun radiation dose (mainly UVB) required to produce sunburn after application of 2mg per square centimetre, divided by the dose of sunlight to produce the same effect on unprotected skin. This translates to a protection factor of 50% for SPF2, 87.5% for SPF8, 93.6% for SPF16, and 96.9% for SPF32.
Sunscreens fall into two categories – inorganic and organic. Inorganic sunscreens act by scattering UV light using zinc or titanium oxides but are generally less cosmetically favourable due to their opaque nature. However they are generally very well tolerated by the skin and produce few allergic effects, thus are recommended for children.
Organic sunscreens actually absorb the UV rays, and as the name suggests consist of a range of complex organic molecules which blend together to give photoprotective qualities.
While many studies have shown that sunscreen protects against acute UV skin damage and non-melanoma skin cancer, whether sunscreen stops melanoma developing has not been conclusively proven.
The authors conclude: “The population has to be advised how to best make use of suncreens. The application of a liberal quantity of sunscreen, is by far the most important factor for effectiveness of the sunscreen, followed by the uniformity of application and the specific absorption spectrum of the agent used.
“Application of organic sunscreens should be done 15-30 minutes before going out into the sun. Waterproof or water-resistant sunscreens should be used to diminish the need for reapplication after swimming followed by towelling, friction with clothing or sand, and sweating.”
Published early online and in an upcoming edition of the Lancet.
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