Frequently Asked Questions
Answered By John Found Dip. Chem., C. Chem., MRACI, MAICD
How are sunscreens regulated?
Sunscreens are regulated as therapeutic goods in Australia and as such must be entered on the Australian Register of Therapeutic Goods (ARTG). The Therapeutic Goods Administration (TGA) ensures that all sunscreens have been tested to the Australian Standard before they are presented for sale. The Standard sets out methods and specifications to ensure that the product meets its label claim.
How are they tested and what does SPF mean?
Before being released on the market each sunscreen is tested on at least 10 human subjects . Firstly, ultraviolet light is applied to the test subjects of 3 different skin types until the first sign of reddening occurs, this is called the Minimum Erythemal Dose or MED. The sunscreen is then applied at the recommended rate and the UV light is applied again until the first sign of skin reddening occurs. The ratio of time in minutes from protected skin to unprotected skin is the Sun Protection Factor or SPF. Therefore, if it takes 10 minutes to make unprotected skin red then an SPF50 product, properly applied, would theoretically offer 500 minutes protection before the skin started to redden.
Chemical or mineral?
Chemical actives and mineral actives must both perform to their label claim so the difference comes down to personal preference. Recent research conducted in Hawaii has shown that some chemical sunscreen actives are responsible for coral damage. There has been a growing trend away from chemical sunscreen actives as a result. By law chemical actives must appear on labels and must be quantified. These actives work by converting incident UV light into heat and are collectively known as solar absorbers. The most common being;
- Octyl salicylate
The move away from chemical solar absorbers has seen an equal rise in mineral sunscreen active products. The main contenders are;
- Zinc oxide
- Titanium dioxide
Mineral sunscreens have a combination of absorption and reflective properties which scatter incident UV light. The chemical or mineral options are regulated by the same mechanism. Each must demonstrate sufficient efficacy to protect against sunburn and UV damage.
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Nano or non-nano?
Mineral actives are available in a range of particle sizes. Nano particles in particular have been a contentious issue for a few years. Generally, a cautious approach is recommended by most scientists especially when there is an opportunity for inhalation. Many health authorities have reviewed the use of nano zinc oxide in sunscreens. They have almost universally decided that they are safe and effective for sunscreen use. The US based FDA have deemed, after an extensive review, that zinc oxide is one of only a few sunscreens that are Generally Regarded As Safe (GRAS).
The damage caused to reefs and wildlife as well as the possibility of absorption of nano particles into the skin have caused a decline in demand for nano sized particles within products. Micronised zinc oxide, which is above 100nm in diameter, is the preferred particle size despite the downside of more “ghosting” on the skin.
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Can a product claim to be nano free?
In any powder there are particles of varying sizes from nano to macro. Particles below 100nm are referred to as nano and occur in relatively small parentages. For this reason a product should not be claiming to be “nano free” or “non-nano” because there is always a small percentage of nano particles present even with the best intentions.
If sunscreens are heavily regulated why do they sometimes fail to work?
Apparent sunscreen failure happens a couple of times a season for every sunscreen brand. Manufacturers typically experience about 2 or 3 complaints relating to each product efficacy per year on average. When we re-test the product we have always found that it met with its release specification and is as functional as it was designed. After several investigations and interviews with complainants, we determined that product failure generally seems to be linked to insufficient application rate, inappropriate use or allergy.
How do we get the application rate so wrong?
Our skin constantly changes tone during the course of a year and is much more sensitive to ultraviolet light in the springtime than it would in mid-summer or autumn. This is largely due to the loss of the pigment melanin during the winter months. As our exposure to ultraviolet light progresses melanin levels in our skin increase and produce a tan. As a consequence, we become more and more immune to low to moderate UV levels as the summer progresses. It is therefore quite common for most of us to be accidently sunburnt in the early summer months. This is because we are used to not taking precautions when exposed to winter sunshine with very low UV levels.
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How does sunburn happen even though we apply sunscreen?
We typically go out into the sun in the spring and only apply sunscreen once we start to feel warm or hot. Unfortunately, on a high UV index day, this is too late to prevent burning because the damage (erythema) has already occurred. Therefore, manufacturers are required by TGA to place instructions on sunscreen to apply 20 minutes before exposure. In addition, the amount of sunscreen applied varies dramatically between individual users and is the primary cause of sunscreen failure. With zinc oxide based sunscreens, we have a habit of rubbing the product in until we can’t see any whiteness. Unfortunately, this is not enough sunscreen to give maximum benefit, the scientifically determined application rate for sunscreens is 2mg of active ingredient per square cm, this may not sound a lot but it’s equivalent to about 20g or 1/5 of a 100g tube of product on a 5-year-old.
Sunscreen sprays, roll on and stick products are less likely to be applied correctly. Once again this is because of our interpretation of how much is enough. The third important aspect of sunscreen protection is re-application. The Australian standard calls for immersion tests that determine the water resistance of sunscreens. Unfortunately the standard does not allow for towelling off or loss by abrasion. This means that the re-application times should be more frequent than recommended if a child is towelled off after swimming. We recommend re-application after each swimming session to our customers.
What part does skin allergy play?
Finally, and somewhat rarely, some individuals have an immune response to sunlight called solar urticaria. This can manifest itself in many ways but typically shows up as a reddening of the skin. The immune response is sometimes stimulated in some individuals by the chemical compounds in sunscreens. It’s usually the fault of fragrance or preservatives. This is not actually sunburn but is the skin’s immune response to ultraviolet light exposure. In a lot of cases, it is typified by the fact that the skin is itchy rather than sunburnt and may sometimes have associated wheals or welts.
Frustratingly, photosensitivity changes with time and amount of exposure, so an apparent severe reaction now may not appear in a couple of months time or when a different product is used. Obviously, the end user would quickly conclude that product “x” doesn’t work while product “y” is fine. This observation is incorrect but understandingly one easy to arrive at.