Tag Archives: Sunscreen

More is more, how much sunscreen is enough?

Despite high SPF50+ sunscreens on the market that are capable of providing hours of protection from sun damage, it’s an unfortunate reality that people continue to become sun burnt while wearing sunscreen. The reasons why we’re still getting sun burnt are simple – we aren’t applying enough sunscreen to properly protect ourselves. Having done some investigation, I was incredibly surprised exactly how important applying the recommended amount of sunscreen is and that applying anything less gives an almost catastrophic reduction in protection.


Sunscreen testing and certification

Before going into detail, it’s worth noting that the sun protection factor (SPF) claimed on packaging have been certified in a laboratory under very detailed conditions relating to the amount of product applied to a surface area (for the technical people, its 2mg/cm-2). For your sunscreen to achieve the claimed SPF, it must be applied in the same manner and for the average adult, this means approximately 36grams (roughly 36mL) for a full body application. For the golfers out there; 36mL is roughly the size of a golf ball in terms of volume, for the chefs/cooks, its 1.5-2 Tablespoons. For those whom are above average in terms of weight or height, they’ll need to use more sunscreen and for those smaller than average (including children) less can be used.

Case Study

To use an example of how poorly this is communicated to consumers, I recently received a customer complaint where an individual believed that their SPF50+ sunscreen was faulty as the family were  sun burnt after using the product.  A detailed investigation found that product was not faulty, leaving consumer misuse as the likely cause.

To set the scene, a husband, wife and three children were holidaying in Queensland, Australia and spent the day at a water park between the hours of 9am to 5pm, using a SPF50+ sunscreen. The questionnaire completed by the parents suggests they followed the product directions and re-applied every 2 hours. An SPF50+ sunscreen should provide 10 hours of sun burn protection if used correctly, more than enough protection for the 8 hours they enjoyed the sun. The reason the family became sun burnt was revealed in the answer to the question “How much sunscreen was used?” the answer;  “half a 100mL bottle”, interestingly  the amount was also described by the consumer as a “liberal” application. Some fairly straightforward math here shows that 50mL used on 5 people would require ~10mL per person all day, with 4 applications, that’s ~2mL each application, does that sound like enough when we’re supposed to being using ~36mL every 2 hours?


Some more detailed math, taking into account the surface area of average  adults and children show that the family used, on average roughly 1/8th of the 36mL used to substantiate the SPF50+ claim. If we  assume that having used 1/8th of the recommended amount, the protection would be 1/8th of the labelled SPF, this equates to an SPF of 7.5 (75 minutes) – insufficient protection for the 8 hours they were out in the sun. The reality however is considerably worse as physics is a cruel mistress, and doing something as simple as halving the quantity applied does more than just halve the performance because absorbance is what is referred to as ‘logarithmic’, bear with me as I attempt to explain.

The quantity of UV light that passes through a sunscreen diminishes more and more as it passes through, a visual explanation is provided below using a SPF 3 (offering 30 minutes of protection) sunscreen absorbing 66% of light and applied in 4 layers to create protection equal to that of a SPF75 sunscreen (offering 750 minutes of protection), 25x more protection than a single layer:


So what’s happening in the above diagram you may ask? The first layer absorbs 66% of the light, transmitting 34%, at this point we focus on what is being transmitted to illustrate, if the second layer transmits 34% of the 34% transmitted by the first layer, then the second layer transmits 11.56% (34% x 34%), the third layer transmits 34% of the 11.56% (11.56% x 34% = 3.93%) and so on and so forth.

The same works in reverse for a sunscreen which has been incorrectly applied as follows:


The above shows that using 1/4 (25%) of the recommended amount of SPF50+ sunscreen (offering 600 minutes of protection) creates protection equivalent to an SPF3 sunscreen (offering 30 minutes of protection). Going back to the original complaint where the consumer was found to have used 1/8th of the recommended amount, the equivalent protection is in fact less than SPF2, it was almost not worth the effort or expense applying any sunscreen!

The below graph may also help to explain the relationship between SPF and applied amount:


There have been a number of studies performed demonstrating how little sunscreen we as consumers apply and that sunscreen performance claimed is rarely achieved. I suggest that the underlying fault lies in the standards used to substantiate SPF where there is a huge difference between the amounts used to measure SPF in the laboratory and that typically used when we’re at the pool, beach or playing sport.

What does it all mean?

It is not necessarily reasonable to expect consumers to fully appreciate the amount we should be applying, we apply what feels right and what feels right is rarely the recommended amount! Logic suggests that the standards used to certify sunscreen should be updated to incorporate an amount that reflects what we use, or at least something more in-line with what we use, such that the claimed SPF is similar to that which we can expect to achieve. Having said that, the implications are that SPF50+ as the maximum claimable SPF isn’t likely to be reduced to account for a lower use amount so it really is up to the sunscreen industry to formulate product the encourages the use of more sunscreen, in the meantime however, we as consumers must learn to apply sunscreen properly.

It is simply not enough just to be wearing ‘some’ sunscreen, particularly if your intention is to be out in the sun for long periods of time, you must apply ‘a lot’ of sunscreen. If we were to think of UV radiation as a bullet with the potential to kill you, sunscreen could be thought of as a bullet proof vest and wrapping ourselves in aluminum foil is not going to stop a bullet… How much sunscreen should you apply, the answer is quite simply ‘a lot’.

And don’t forget to re-apply frequently!

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SolarD, Vitamin D and Sun Protection


SolarD sunscreen was introduced into the Australian market in late 2014, advertised as being a technologically advanced formula that permits the particular wavelengths of ultra-violet light that your body uses to naturally produce vitamin D. The concept for this product is new and no doubt of interest to consumers with the increasing concerns over their vitamin D levels and reports that regular sunscreens prevent vitamin D production. Without suggesting that people should avoid using SolarD, I do feel that it should be used with caution and appropriate consideration for their sunscreen needs, lifestyle and the recommendation of their doctor.

Importance of vitamin D

Vitamin D, as with all vitamins are essential to our health, vitamin D helps the absorbtion of minerals including; calcium, iron, magnesium, phosphate and zinc, all of which are critical to bone health. Being deficient in vitamin D can cause rickets, osteomalacia and osteoporosis and has been linked to cancer, various auto-immune, cardiovascular disease and mental health.

The recommended daily amount (RDA) of vitamin D for adults who do not have a vitamin D deficiency is 600IU, this is equivalent to 0.0000015g (15µg).

Sources of vitamin D

There are two types of vitamin D, D2 and D3; vitamin D2 is found in mushrooms and ‘fortified foods’ such as milk, margarine and breakfast cereals where the vitamins have been artificially added. Sources of vitamin D3 include foods such as salmon and other oily fish, eggs and milk in addition to fortified foods and vitamin D supplements, vitamin D is also produced through sun exposure.

Vitamin D3 is the most potent and effective type of vitamin D with sun exposure being the most efficient means of attaining our vitamin D3.

The most concentrated dietary source of vitamin D is found in wild salmon which has up to 1000IU of vitamin D3 in every 100g. Turns out that a salmon a day could keep the vitamin D deficiency away, unfortunately, eating salmon everyday is not great for a balanced diet, which is why sun exposure is important.

Vitamin D3 and sun exposure

Producing vitamin D3 through sun exposure is a complex reaction that occurs within our skin, requiring sun light to drive the reaction, specifically the wavelengths of light between 270 and 320nm. Visible light are those wavelengths between 390-700nm, as the wavelengths of light required to produce vitamin D3 are below those of the visible, they are ‘ultra-violet’ (UV) wavelengths which we can call UV light.

The amount of vitamin D3 produced when exposing ourselves to sun light will vary considerably with the amount of exposed skin, age, height, skin color, time of day, season, longitude and altitude, from as little as a few minutes in summer, to a few hours in winter. Interestingly, the amount of vitamin D generated in the skin is limited, to the point where longer exposure to sun light will not necessarily increase our vitamin D levels, unlike the risk of skin damage and skin cancer which will increase the longer we spend in the sun.

Causes of sunburn and the vitamin D paradox

Ultra-violet B (UVB) light refers to those wavelengths of light between 280 and 315nm, Ultra-violet A (UVA) are those wavelengths between 315 and 390nm. The UVB wavelengths are most responsible for causing sunburn, but are also responsible for causing skin cancer and other sun damage, particularly premature ageing such as wrinkles and sun spots. The method used to test the sun protection factor (SPF) of a product uses sunburn as the endpoint to determine whether the product is providing protection simply because the sunburn is an indicator of sun damage that is (close to) immediately visible and easily measured.

You may now note that the wavelengths of light that are required to produce of vitamin D3 detailed above are the same as those that cause sunburn. A sunscreen that is aimed to prevent sunburn and that is promoted to permit the particular UVB light that your body uses to naturally produce vitamin D3 should be physically impossible.

A look at how Solar D works

The UV absorbtion spectrum of SolarD SPF50 sunscreen in comparison to a regular SPF50+ Sunscreen (below) shows SolarD absorbs less light in the UVB (280 – 315nm) region than a standard sunscreen, which goes to justify the claim that SolarD permits the particular UVB light that produce vitamin D3, but doesn’t necessarily support the SPF50 claim.


How does SolarD make sun protection claims if there isn’t enough UVB absorbtion to prevent sunburn?

Before I go into any further detail and to place the remainder of this article in context, I must highlight that I am not aware of SolarD’s technology or formulation so I do not know with any certainty how SolarD achieves their claims. Being involved in the development of sunscreens (as I am) and having been aware of the health issues surrounding vitamin D, I had already considered ways that a sunscreen can promote vitamin D production and protect against sunburn, they are unusual and in my mind, not necessarily in the consumers best interest.

Sunburn is only one symptom of sun exposure, it is the one we readily relate to as we see and feel it so soon after we have been in the sun, other symptoms include skin cancer and premature ageing such as wrinkles and sun spots. We often treat sunburn using after sun products containing anti-inflammatory ingredients such as aloe vera and green tea and also anaesthetics like lidocaine, but these products won’t undo the damage that has already been caused, only reduce the redness/pain we can see and feel.

A sunscreen could, in theory, have a high sun protection factor (SPF) without the need for the product to absorb a lot of UV light by treating the visible symptoms of sun exposure we know as sunburn. A product such as this would be reliant on those same anti-inflammatory ingredients used in after sun products to compensate for a reduction in UV absorbance relative to that of a normal sunscreen. The issue here is that by failing to absorb as much UV light, more damaging UV light will be allowed to pass through to the skin where damage will occur despite the sunburn having been masked by the ant-inflammatory action. We could liken this to spraining your ankle whilst on pain and anti-inflammatory medication, the damage was done, the ankle is now weak and unstable, we just can’t feel it and in no way was the damage prevented.

I am not suggesting that this is how SolarD functions, without seeing the product technology in its entirety; this is only my theory on how the product may perform and something worth being mindful of.

Vitamin D production vs sun protection

The primary purpose for any sunscreen is to minimize sun damage by absorbing the UV light and reducing the risks of sunburn, skin cancer and premature ageing when we’re out in the sun. Realizing that sunscreens have an obvious potential to alter the way vitamin D3 is formed and influence vitamin D deficiency and related diseases, we need to instill a balanced approach so that we get enough sun exposure to allow vitamin D production, but not so much as to cause sun damage.

While wearing a regular SPF50+ sunscreen in summer will slow the formation of vitamin D3, the small amount of UV light which does pass through over the period of a few hours will generate the same amount of vitamin D3 as spending a few minutes without sunscreen with the added benefit of their being less risk of damaging the skin and there have been studies that show this to be the case.

We should all use sunscreen whenever there is a risk of sunburn, if there is no risk of sunburn, there is no need to wear sunscreen, if in doubt though, your best to have sunscreen on. If you’re going to be outdoors outside peak sunburn times (early morning or late afternoon) or only for very short periods during the day, there is no need to apply sunscreen, by doing so, our bodies will be produce vitamin D3. For those who have concerns relating to premature ageing such as wrinkles and sun spints and prefer to wear sunscreen at all times, then SolarD may be a good option to minimize damage without inhibiting vitamin D too much, a lower SPF sunscreen would however have a similar effect.

For those who are planning on spending a lot of time in the sun, especially at the beach, pool or playing sport, your best to wear a 4 hour water resistant SPF50+ sunscreen for maximum protection, remembering the sunscreen will allow vitamin D3 to be formed. I stress this point because SolarD, being a 2 hour water resistant SPF50 sunscreen has 15-20% less SPF and half the water resistance of a 4 hour water resistant SPF50+ which is not going to provide the best protection.


To buy SolarD or not to buy SolarD

I don’t want to discourage people from using SolarD, it’s an interesting concept that will have a place on the market, however it does complicate the decision making process, particularly for those who believe their existing sunscreen is somehow less effective in terms of allowing vitamin D production to occur.

If you haven’t been diagnosed with a vitamin D deficiency, then your current lifestyle and existing sunscreen habits are working for you, there is no need for a product like SolarD. For those who have been diagnosed with a vitamin D deficiency, your doctor would offer the best solution with consideration for minor lifestyle changes to get more sun, using vitamin D supplements and perhaps recommend SolarD.


  1. Olds, 2010; Elucidating the Links Between UV Radiation and Vitamin D Synthesis; Using an In Vitro Model, Queensland University of Technology.
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MythBusting SPF50+ Sunscreens


With the introduction of SPF50+ sunscreens into Australia in late 2012, early 2013, there had been, and continues to be, a belief by some (including some fairly reputable organizations), that there is a negligible increase in protection as compared to previous generation SPF30+ sunscreens. Given SPF is the acronym for ‘Sun Protection Factor’, logic should prevail that 50+ provides considerably better protection than 30 and it is, twice as good in fact!

The articles that have been written dismissing SPF50+ will always raise a supposed minor change in protection by referring to a “1.3% increase in protection” which is an incorrect representation of a factual figure. There is a 1.3% increase, however the increase relates to the absorbance, where SPF30 sunscreen absorbs 96.67% of UVB radiation (and plenty of UVA also), whilst SPF50 sunscreen absorbs 98.00% of UVB radiation (SPF50+ actually absorbs over 98.33%). If we presume an SPF30 sunscreen was to provide 300 minutes of protection, an SPF50 sunscreen certainly does not offer a paltry additional 3.9 minutes in the sun (300 minutes multiplied by the supposed “1.3% increase in protection”).

Absorbance is a measure of a physical property of a sunscreen, a moment in time, the missing piece of the puzzle, the piece that is used in calculating the SPF of a sunscreen, is time. Attempting to measure protection by referencing absorbance alone is like trying to measure speed by referencing distance and not accounting for time, something that would have Galileo rolling in his grave.

What is more critical for a sunscreen in terms of protection is not what the sunscreen absorbs, but what is does not, this is referred to as transmission, the amount of UV radiation that is not absorbed and has passed through the sunscreen onto the skin where it can cause damage. If an SPF50+ sunscreen transmits 1.67% (100% – the 98.33% absorbed) and an SPF30+ sunscreen transmits 3.33%, it quickly becomes obvious that the SPF50+ is transmitting half the amount of UVB radiation through and absorbing 200% more UVB radiation, that 1.3% sounds like allot now!

If the average person burns in 10 minutes, the amount of time a person can spend in the sun before becoming sun burnt (and would be considered ‘protected’) can be determined using the following simple equation:

Time = 10 minutes / Transmission (%)

Now let’s apply that to some SPF values:

  • SPF0 – Not a valid SPF
  • SPF1 – 10 minutes (no protection, calculated on 100% transmission), realizing this is not an valid SPF from a product perspective, but our skins natural protection factor.
  • SPF2 – 20 minutes
  • SPF30 – 300 minutes
  • SPF50 – 500 minutes
  • SPF50+ – 600 minutes

Now in graph form:


Its worth keeping in mind that the above calculations assume the sunscreen is used appropriately, which it often isn’t and this is largely the reason why SPF50+ sunscreens are being made available, to account for improper use (I’ll discuss this more later, suffice to say, people are still getting sun burnt!).

Amanda at Realize Beauty offers a more visual explanation on her blog.

Some examples of websites and organisation promoting ‘The Myth’:

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