What is important when buying sunscreen from the formulator's point of view?
The checklist:
1. High UVA protection.
2. Photostable sunscreen!
3. Formulation that will stay on the surface of the skin rather than sink in.
4. And a formulation that is pleasant to use.
1.UV Rays
It has been stated that UVA protection is equally important as UVB protection.
Let me explain a bit about UV rays. UV rays can be grouped into 3 subcategories:
UVC (up to 290nm) filtered out by the Ozon-layer. Highly cancerous.
UVB (290-320nm) which are high energy rays. Only 5% of all rays reaching the surface of the Earth are UVB rays.
UVA (320-400nm) which are low energy rays. 95% of all rays reaching the surface of the Earth are UVA rays. They are almost constant all year around. They weaken our immunsystem.
UVA rays can be grouped into to subcategories:
UVA2 (320-360 nm) or short UVA.
UVA1(360-400nm) or long UVA.
What do these rays do to our skin?
UVB makes our skin burn (B for burning), makes our body produce melanin (our natural protection against UVB-rays). It has an equivalent of SPF4 in a white person which is a very low protection. It will still allow the skin to let 25% of UVB rays pass through our "natural" protection.
Since they are short waves they do not penetrate deep in the skin. It reaches mostly our Epidermis.
They are dangerous because they can increase the chances to have skin cancer especially if one burns before the age of 18: AC and SCC, BCC.
UVA rays are even more dangerous than UVB. (A for Aging)
It is very recent that it has been generally acknowledged that UVA rays are dangerous.
It has been widely believed that UVA rays were harmless and there was no need to protect the skin against them.
We now know better than that.
For years it has been only necessary to produce sunscreens that protected against UVB rays. Hence the SPF marking on the sunscreen-bottle will refer to its protection against UVB rays.
(The higher the number the better the protection).
What is not universally agreed (yet) is how to define UVA protection of a sunscreen?
How do I know as a costumer that the sunscreen actually protects against UVA?
There is no law that will determine that a sunscreen should protect against UVA rays (except in Japan and in Australia, though not the whole UVA range).
What we know today about UVA rays is that they penetrate much deeper in the skin (Dermis). They are the main cause of a wrinkled, photo-aged appearance.
They destroy our precious collagen and elastin fibbers which give our skin its support and suppleness.
We also know that while UVB rays cause direct damage to our DNA, UVA causes indirect damage to our DNA. Which is believed today to be the main cause of Malignant Melanoma, the deadliest from of skin cancers.
So when we buy a sunscreen it is equally important that it has a high protection against both UVA and UVB rays.
Ideally a sunscreen should have the same protection value against UVA as against UVB.
To be able to achieve this a formulator has to have good UVA sunscreening agents (that are only available in the EU, partially in AU and JP). OR: formulating a bad sunscreen that will have high UVA protection because the agents low reflective index in the UVB-zone. (Like ZnO alone).
It is crucial to use good UVA filters that also filter in the UVA1 area (360-400nm).
Let me say some words about regulations of sunscreens in the World:
EU: it is only a recommendation: Sunscreens should provide protection both in the UVB and UVA field. The value of the UVA protection of a sunscreen should be at least 1/3 of the SPF (UVB protection). The critical wavelength of the UVA protection should be min.370nm.
AU: Sunscreens must protect in the UVA range of 320-360 with a maximum transmission of 10%.
US: Sunscreens can be formulated as Broadband protection. No specifications are given about neither what Broadband protection is nor how much of the SPF value the UVA protection should be.
The second problem is that not all UVA filters are available/allowed by the law of the region everywhere.
While in the EU one can formulate a good and photostable sunscreen with very high UVA protection without the need of using a lot of chemicals it is considerably more difficult elsewhere.
And in my opinion it is impossible in the US given the allowed UVfilters and their combination possibilities. (AVO cannot be combined with inorganic filters).
One also has to think of that these organic filters should be compatible with each other and have a synergetic effect and be photostable. So one can use the minimum amount of chemicals for greater effect!
2.Photostable sunscreens
The composition has to be photostable giving a real protection for up to 2 hours in sunlight.
So as you can already see it is not an easy job!
What one should look for on the label is UVA filters:
AVO (has to be combined with either OCR, Polysilicone-15** or TinosorbM* or S** to be able to stabilize it!)
TinosorbS** and/or M* (they are UVB, UVA2 and UVA1 filters)
Mexoryl XS (UVA2)
Mexoryl XL* (UVA1)
ZnO (UVA2+1) but it should be combined with either TiO2 and preferably with other UVA+UVB filters!
*available in the EU, partially in AU, JP; not at all in the US!
** Available only in the EU.
In short: one has to buy a sunscreen that is sold in the EU. And preferably that contains Tinosorb S (and M).
Tinosorb filters have much greater filtering abilities than the patented Mexoryl filters! And freely available for any formulator in the World! (Mexoryl was patented by L'Oreal 1993 and 1998).
Tinosorb M and S are products of the Swiss based Ciba Speciality Chemicals that created these filters in 2005.
Today they are used in countless brands in the EU, like Nivea and Avène.
When combined with AVO (which is stabilized by them) and other UVB filters: TiO2 and/or OMC one can achieve a well balanced sunscreen that will protect both in the UVB and UVA2 and 1 range.(OMC also gets stabilized by these filters and its destabilizing effect on AVO disappears).
3. The Base
Many sunscreens unfortunately are poorly formulated even though they contain very good UVA filters.
There is a rule in formulating topical products that the size of the molecule should be smaller than 500Dalton to be able to penetrate into the Epidermis.
And it is a great rule! As long as the aim is to transport active ingredients into the Epidermis ( VitE) or deeper (Tretinoin).
But sunscreens should not be transported anywhere in the skin! They should remain on the surface of the skin to be able to protect fully.
If they penetrate in the skin then they will not scatter UV light away from the skin but within the skin hence doing more harm than good!
Today there are many scientists that believe that we should not follow the 500Dalton rule when it comes to sunscreens.
To be able to achieve a film on the surface of the skin rather within the skin (like a good moisturizer should) it is essential to use big molecules like silicones.
Dimethicone, Simethicone, Cyclomethicone; siloxanes etc should be high on the ingredients list to be able to make that the sunscreening agents will stay on the surface of the skin.
One could of course formulate with MicroBeads (AVO+OMC in dimethicone) tha will also make it possible to have a film like effect on the skin.
4. Pleasure
It is still not enough to have achieved all this: good UVA protection, photostability and a film on the surface of the skin.
The product has to be pleasant on the skin. It should not sting the skin (Mexoryl SX, XL and OCR tends to sting the eyes and the skin especially if one is on Acne treatments like Tretinoin or Azaleic Acid).
It should not make the skin greasy or shiny exaggerating pores and inperfections. (Mexoryl SX, XL, OCR and TinosorbM tends to do all this).
A good sunscreen should be matte hence minimizing the size of pores and imperfections (Silicone will do all this! If ZnO or TiO2 in higher amount is added the effect will be even greater and will last the whole day.)
List to remember:
Full UVA protection (EU filters preferably TinosorbS,M) (High SPF better chance to have higher UVA protection)
Silicone
TiO2 and /or ZnO
Photostable
Remember to reapply your sunscreen every 2h throughout the day!
One more advice:
Find out where you can check the daily UV-index for the area you live in. Remember the UV index applies for UVB rays (UVA is always higher!)
Avoid sun exposure all times as long as it is possible!
Avoidance is crutial
Cover your skin with thickly woven coloured clothes
Wear a broad rimmed hat and big sunglasses
Use a sunscreen all exposed skin
5.Sunscreens in the Future
All sunscreens will be like what I described now! J
With enhanced UVA protection by naturally occurring substances (Antioxidants).
On the package you will be able to see the performance graph of the sunscreen and the transmission graph so you'll be able to see how much UV rays the sunscreen allows to reach your skin in each spectrum.
6. Numbers
We should not think in numbers when it comes to sunscreens. Like an SPF 15 filters 93% of all UVB rays, or SPF20 filters 95% etc. Instead we should think like an SPF 15 allows 7% of the UVB rays to reach my skin, SPF 20 will let 5% of UVB rays reach my skin!
I should use a sunscreen that will protect my skin the most! That will allow very little light through (like an SPF50/50+ UVA 35+).
For further reading please see:
On silicones:
http://en.wikipedia.org/wiki/Silicone
On sunscreens:
http://en.wikipedia....een_controversy
http://en.wikipedia....nning_activator
Attached Files
Edited by Eva Victoria, 29 June 2008 - 08:13 PM.