A bit about sunscreens

With spring well and truly here, and summer fast approaching, I thought it might be a good idea to remind people about using sunscreen while you are outdoors enjoying exercising in the sun. Of course, you should be using sunscreen all year round whenever you are outdoors; but with the warmer weather and the sun being a little more fierce, at this time of year its more important than ever!



Statistics from Cancer Australia estimate that almost 14,000 new cases of melanoma will be diagnosed across 2017, which accounts for approximately 10% of all new cancer cases in Australia. Cancer Australia also estimates that there will be close to 2,000 deaths in 2017 as a result of melanoma, which accounts for almost 4% of all cancer related deaths.


Obviously, these figures are a little bit alarming. With everything we currently know about cancer and cancer avoidance, this many new cases of melanoma diagnosed each year is too many….it seems that a lot of people are still not getting the message about skin protection when out in the sun.


Invisible UV radiation from the sun comes in different wavelengths, ranging from 100nm up to 400nm. These UV rays are divided into 3 different groups depending on the different wavelengths.

UV-C rays range from 100nm to 290nm. As they are completely blocked by the ozone layer, UV-C rays will have no effect on your skin….they are only an issue if you use a tanning bed (which you should never, ever do!).

UV-B rays exist between 290nm to 320nm. These rays are partially blocked by the ozone layer and are unable to penetrate glass. However, when they do reach the skin, they are the most damaging form of UV radiation. UV-B rays are primarily responsible for sunburn and lead to skin cancers; so they are the main rays which are targeted by sunscreens. UV-B rays account for about 5-10% of the UV radiation which reaches the earth’s surface.


UV-A rays are the longest, from 320nm to 400nm. UV-A rays are not stopped by the ozone layer or glass at all; and are able to penetrate the skin deeper than other UV rays. They are typically responsible for causing age spots, wrinkling and other signs of premature ageing. They have also found to be responsible for causing skin cancers. 90-95% of the UV rays reaching the earth are UV-A rays.

When UV radiation hits your skin, the energy from that radiation has to go somewhere. Without sunscreen, it goes into the fats and proteins within your skin; causing cellular damage. When the cells are damaged, your body produces an inflammatory response. Blood vessels dilate, sending more blood to the area (resulting in redness and swelling), and proteins (known as cytokines) are produced. This result is, of course, painful sunburn.

In addition to sunburn, the UV radiation can cause some changes to your DNA. As your skin has a high turnover of roughly 28 days, there is a chance that these changes, or mutations, to your DNA will be passed along to newer cells. These mutations are the cause of skin cancer.


When sunscreen is applied properly, it is designed to stop this dangerous UV radiation from damaging your skin. There are typically 2 different types of ingredients in sunscreens…..organic (chemical absorbing) and inorganic (physical barrier).

Organic ingredients (including oxybenzone and aminobenzoic acid) are named purely because they are carbon based…usually they contain a carbon ring. When UV radiation hits these carbon rings, the bonds holding the carbon together absorb the energy from the UV rays, and release it in the form of heat (which, no, will not make your skin noticeable warmer!).


Inorganic ingredients (zinc oxide) are not carbon based. They still absorb a small amount of energy from UV radiation, but they primarily work by deflecting the UV rays away from the body. Previously, these ingredients typically resulted in a thick, white layer of cream covering the skin; but modern “micronising” techniques have allowed them to be broken down to appear invisible, without losing their effectiveness.

Most sunscreens contain a combination of both organic and inorganic ingredients. Most of the organic ingredients used are effective against UV-B rays; while the inorganic ingredients are usually effective against both UV-A and UV-B rays.


SPF stands for Sun Protection Factor, which refers to protection against harmful UV-B rays. It is a reference to how much longer it will take for damage to occur, compared to wearing no sunscreen at all. For example, if it normally takes 10 minutes for skin damage to take place, a correctly applied SPF30+ sunscreen will hypothetically mean you have 300 minutes instead.


But its not as simple as that. An SPF15+ will only block about 93% of harmful UV-B rays, while an SPF30+ sunscreen will block 96% of them. At an SPF50+, 98% of UV-B rays are blocked….above this, any increase in SPF protection is minimal. Hence, here in Australia, SPF has been limited to 50+.

In addition, SPF does not refer to the protective benefits against UV-A rays. To ensure your sunscreen protects against both UV-A and UV-B rays, check that it states “Broad Spectrum” on the label….although sometimes it may simply state the fact that it protects against both types of radiation!


Unfortunately, most people simply don’t apply sunscreen correctly. Ideally, you should be applying 2mg of sunscreen for every square centimetre of skin….but most people only use about a quarter of this! Ultimately, this means that most people achieve an SPF which is much less than the labelled figure.

One of the better recommendations I have seen is to use a shot glass. For an average adult, approximately one and a half shot glasses full of sunscreen is needed to effectively cover the arms, legs, torso and face. Think about it…..are you using this much???


Sunscreen should be applied to the skin at least 15 minutes before you head outside. This way, the skin has time to actually absorb the sunscreen, and it can start working the instant you head outdoors.

The other way people reduce the effectiveness of their sunscreen is by not applying it often enough. Although an SPF of 50 may mean that you can potentially have more than 8 hours of protection; sunscreen does in fact wash off! Water and sweat mean that sunscreen does not stay on the skin as long as it needs to……its always a good idea to reapply sunscreen every 2 hours if possible.



Creams, lotions, milks, sprays…..there are a lot of options on the market! Ultimately, as long as what you are using contains ingredients which protect against both UV-A and UV-B radiation (broad spectrum), and it has an SPF of 50+, you are on the right path.

Ensure that you apply your sunscreen properly, reapply it every 2 hours and keep your skin covered as much as possible….and hopefully you can avoid any harmful damage from the sun while you are outdoors!

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