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Sunscreens

Sunscreen product

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Australia has one of the highest rates of skin cancer in the world, with two out of three Australians developing some form of skin cancer during their lifetime.

Continuous exposure to ultraviolet radiation (UVR) may lead to premature ageing of the skin and eventually skin cancer. Using properly applied sunscreen of at least SPF 30 is an important preventative measure to help reduce these risks.

Sunscreen should be used in conjunction with other precautions such as:

  • reducing the total amount of exposure to the sun, especially during the peak UV period (typically from 10am to 3pm local time)
  • wearing appropriate sun protective clothing, including broad brim hats and sunglasses
  • making use of shade.

The Australian standard has been revised for sunscreens, which now allow a SPF rating of 50+, however no sunscreens are 100 per cent effective, and an SPF 50+ sunscreen is only ever so slightly (1.3%) more effective than one rated at SPF 30. Applying a sunscreen properly is much more important than whether it’s rated at SPF 30 or 50+.

Sunscreen Effectiveness

The effectiveness of sunscreens is dependent upon how thickly and frequently the sunscreen is applied to the exposed skin.

How much should be applied?

The internationally accepted application thickness is about 2mg per square cm(1). It takes about 30ml (approximately six teaspoons) of sunscreen lotion to protect the entire body of an average adult. So a 120ml tube of sunscreen should only last four applications.

Sunscreen should be applied to all exposed areas of dry clean skin not covered by clothing at least 15 to 20 minutes before going outside and then reapplied to achieve a more optimum level of protection. The reapplication is necessary as most people don’t apply enough, resulting in only 20 – 50 per cent of the SPF rating.

Reapplication does not give additional protection but ensures that the stated protection is achievable.

People may still suffer sunburn after using high SPF rated sunscreen if they:

  • apply insufficient amounts of sunscreen
  • miss applying to an area of the skin resulting in overexposure while believing they are protected
  • fail to immediately reapply sunscreen after swimming, heavy perspiration, or towelling dry
  • fail to reapply sunscreen every 2 hours.

SPF Rating

A sunscreen’s SPF rating indicates the level of protection provided against UVR. It’s the ratio of the UV radiation dose required for perceivable sunburn on skin applied with the sunscreen compared to unexposed skin.

No sunscreen products including those with 50+ rating provide 100% protection against UV radiation.

Sunscreens sold in Australia must be labelled with an SPF of at least 4 to 50+. Sunscreens with less than SPF 15 offer low protection whilst SPF 50+ offers very high protection.

Sunscreen protection of SPF 30 for a fair skinned person provides 30 times more protection to the exposed skin; if the skin reddens without protection in 10 minutes, then applying SPF 30 sunscreen provides protection for up to 300 minutes if applied correctly.

The purpose of using sunscreens is to reduce UVR exposure, not to extend the time spent outside in the sun.

The following table shows that a broad spectrum sunscreen with SPF 30 blocks 96.7% UVR and a SPF 50 blocks 98%. This is only a marginal increase in the UVR blocked by the sunscreen.

SPF % UVR Blocked
4 75
8 87.5
15 93.3
30 96.7
50 98

The composition of sunscreens

Sunscreens may consist of, chemical absorbers, physical blockers or both.

Chemical absorbers in sunscreen absorb the UV radiation and stop it from reaching the skin. The physical blockers (titanium dioxide and zinc oxide) are fine particles (nanoparticles) that stay on the surface of the skin to reflect and scatter UV radiation acting as a physical barrier. Generally physical blockers are considered safer and more effective than chemical absorbers for their broad spectrum UV radiation blocking ability.

There has been concern regarding nanoparticles being absorbed by the skin and harming living tissue. The TGA’s review(2) concluded that ‘the current weight of evidence suggests that nanoparticles do not reach viable skin cells and remain on the surface of the skin and the outer layer of the skin that is composed of non-viable cells’.

There may be short term effects from using sunscreen for people with sensitive skin. Short term effects may include skin irritation, stinging or a rash.

In Australia sunscreens can only be sold if they are listed on the Therapeutic Goods Administration (TGA) Australian Register of Therapeutic Goods (ARTG) and are compliant with the standard AS/NZS 2604:2012. Sunscreen active ingredients and maximum concentrations are approved by the TGA as being both safe and effective.

The revised sunscreen standard

The revised Australian sunscreen standard (AS/NZS 2604:2012 ‘Sunscreen products – Evaluation and classification’) limits the maximum protection claimed on the labelling of sunscreen products to SPF 50+. The move to increase the SPF limit to 50+ was partly due to technological improvements in the composition of the sunscreens.

Sunscreens are available as either a primary or secondary sunscreen.

  • Primary sunscreens are a product primarily to be used to protect the skin from UV radiation.
  • Secondary sunscreens have a function other than skin protection from the sun whilst still providing some protection of the skin from UV radiation i.e. moisturisers, make-up, lip balm, anti-ageing, anti-wrinkle creams.

The major changes to the standard are:

  • The raising of the SPF limit to 50+
  • new method of measuring broad spectrum properties
  • modification to the method of measurement of SPF to bring it in line with international practice
  • changes to classification of sunscreens due to the new limits to SPF
  • new requirements for satisfying the claim of broad spectrum.

Sunscreen manufacturers are unable to claim the terms ‘sunblock’, ‘waterproof’ and ‘sweat proof’ as these terms are considered to be potentially misleading. The maximum water resistance claimable is 4 hours for SPF 30 and above.

References

  1. AS/NZS 2604:2012 ‘Sunscreen products – Evaluation and classification’
  2. Department of Health and Ageing - Therapeutic Goods Administration (http://www.tga.gov.au)
    ‘A review of the scientific literature on the safety of nanoparticulate titanium dioxide or zinc oxide in sunscreens’

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