Why Mineral Powder Sunscreen Will Never Give You Sun Protection
Mar 04, 2021
Australia has one of the highest skin cancer rates in the world and yet unfortunately the use of sunscreen is declining. Despite education regarding the importance of sunscreen use, the average consumer does not apply anywhere near the required amount of sunscreen to be adequately protected. Consumers also often only rely on sunscreen and do not use other methods of protection from the sun such as hats and avoidance of specific times of the day. Consumers unknowingly are not using sunscreen correctly, nor do they understand the principles of how it works. In order to be adequately protected you need to understand how sunscreen works and how to use it so that you are sufficiently protected.
The two most commonly used inorganic sunscreens are titanium dioxide (Ti02)and zinc oxide (ZnO). The microfine powders, used in sunscreen products, have an average particle size of approximately 0.20 pm (micron) or less. Each particulate has a size at which it maximally scatters visible light. This is the ideal size for use as a white or colored pigment. As a sunscreen, however, any color rendered to the product by an ingredient is undesirable. Thus, the average particle size of a metal oxide is reduced below the optimal light scattering size, allowing visible light to be transmitted and therefore, appearing virtually invisible on the skin. Zinc oxide or TiOz used in sunscreen preparations is often coated with other materials such as silicones, fatty acids, or oxides of aluminum, silicon, or zirconium to aid in dispersion.
Substances such as zinc oxide and titanium dioxide offer physical protection in that they are opaque enough to reflect and scatter the incident radiation. Photon-absorbing agents function by absorbing radiation in the ultraviolet region and then undergoing very rapid vibrational relaxation back to the ground state. Once in the ground state, these molecules can absorb another photon to repeat the process, thereby effectively shielding the skin from damage by UV radiation. Any molecule for which vibrational relaxation to the ground state is the fastest pathway can act as a sunscreen.
SPF ratings are calculated based on a certain amount of sunscreen being applied. In order to get the SPF stated on the bottle is only achieved by applying 35mls to the entire body, which equates to 7 teaspoons of sunscreen. If it’s put on too thinly the protection is lessened and it won’t work as well. A greater SPF does not mean that less sunscreen needs to be applied or that you can stay in the sun for a longer period of time. SPF is a rating of what percentage of UV rays the sunscreen protects you from.
So let's put this in perspective and compare a sunscreen cream versus a powder. A typical cream sunscreen that is mineral contains approximately 25% Zinc Oxide in a 100ml tube. You need to apply 2.7 ml to the face and decolletage to get the advertised SPF value. Even if you were to only do the face and halved the amount you would still need 1.35mls being applied to get SPF 30.
A cream product generally comes in a package ranging from 40ml to 500ml in size, but regardless of the size you still need to be putting 2.7mls for the face and decolletage area.
So here is where it gets interesting. Taking a look at a typical powder sunscreen such as Brush on Block.
The container is a teeny weeny 3.4 grams. Even though they still have a similar listed w/w percentage of sunscreen ingredients you still need to use 2.7 grams of this powder to get the SPF.
So in the 3.4 grams total there is
3.4 x 14.7% = 0.4998 grams of Zinc Oxide
3.4 x 13.8% = 0.4692 grams of Titanium Dioxide
So this is the total percentage of sunscreen ingredients in that tiny container.
There is absolutely no way that you are going to use 2.7 grams of powder on your face. You would look like something from a horror movie. You would also go through the container in under 2 days!!
Sunscreen in powder format is just not feasible and still, the FDA and TGA have not approved it as it a form that is recognised on the sunscreen monograph.
So don't fall for the powder sunscreen trap. Your clients are not protected. Whilst it may seem convenient, in life most things that seem too good to be true usually are.
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