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What does the UV Index mean?

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The UVI (Ultra Violet Radiation Index) is a tool that helps us determine the amount of sunscreen we need to apply and whether or not we need to implement sun-smart practises. But what does the UV and UVI actually mean?

According to the WHO (the World Health Organisation) website, the UVI is "a measure of the level of UV radiation. The values of the index range from zero upward - the higher the UVI, the greater the potential for damage to the skin and eye and the less time it takes for harm to occur".

The UVI is an important tool for us to understand the danger of ongoing sun exposure; it provides a comprehensive indication of the level of harm each day offers, and reminds us lf the appropriate measures that need to be taken.

The 'index' part of the UVI refers to a table created 20 years ago for use in most European countries and North America, where extreme weather conditions are less frequently experienced. This index was developed through the combined efforts of the United Nations Environment Program, the World Meteorological Organisation and the WHO.

UV Index Range WHO Recommended Action
1 – 2 (Green) No protection required. You can stay safely outside
3 – 5 (Yellow) Seek shade during midday hours! Slip on a shirt, slop on sunscreen and slap on hat!
6 – 7 (Orange)
8 – 10 (Red) Avoid being outside during midday hours! Make sure you seek shade! Shirt, sunscreen and hat are a must!
11 + (Purple)

According to the BBC, a German physicist, Johann Ritter, discovered ultraviolet in 1801. His findings, in conjunction with the discovery of infrared light by British astronomer William Herschel a year earlier, proved the existence of invisible light beyond both ends of the colour spectrum.

In tackling the nitty gritty of UV, or ultraviolet radiation, breaking down its components provides an explanation of what it is, and why it is harmful. As we know, ultraviolet light is invisible; it is a type of radiation that contains shorter wavelengths made up of 'UVB' and longer wavelengths called 'UVA'. UVB has a higher energy than UVA. For non-science enthusiasts, the most important thing to remember is that both UVA and UVB have harmful effects on skin cells, and are strongly believed to be catalysts for the inception of skin cancers, including melanoma.

However, UVA are UVB are two different types of UV rays; the former is a more likely to cause sunburn, resulting in changes to the dermis' pigmentation and the latter is more likely to penetrate to a deeper level of skin causing wrinkles and other forms of ageing in the dermis. Failure to use SPF50+ sunscreen and wear sun smart clothes will result in increased exposure to harmful UV rays.

Whether or not you are a sun-smart person, it is important to continue to look for any changes to your skin.

Book an appointment at a SunDoctors’ clinic in NSW, Queensland, Victoria or South Australia. Otherwise, call 13-7546 (13-skin) to find your closest clinic and book an appointment.

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