In the last sunblocks/ sunscreens post, I only talked about SPF which tells us how much the sunblock can protect us from the damage of UVB rays.
After a talk with a colleague today, I realized that I left out the protection factor for UVA rays.
So is there a protection factor for UVA rays that is used by the manufacturers?
Currently, there is no consensus regarding an ideal method to assess protection against UVA radiation.
The UVB rays readily causes redness of the skin which allows assess of protection to be easy. UVA rays can cause redness of the skin only after a much larger dose.
If you see some sunblocks/ sunscreens having PA++ on the packaging, it is saying that the product can protect you against UVA rays.
PA stands for Protection Grade of UVA. There is currently no uniform measure of UVA absorption, so PA is only a rough indicator of the amount of UVA protection the suncreen offers.
There are three grades, namely PA+, PA++ and PA+++.
PA+++ offers the most protection. PA+ is adequate for most activities. If you’re staying out in the sun for long hours, go for PA++ or higher.
There are actually 4 methods being used to measure the protection effect.
1. PPF-method (Phototoxic Protection Factor)
2. APF-method (Erythemal UVA-protection Factor)
3. IPD-method (Immediate Pigment Darkening)
4. PPD-method (Persistent Pigment Darkening) or PFA (Protection Factor UVA)
APF and PPD methods are more recommended for determining the UVA protection level.
APF: Similar to SPF asessment method, testing how fast the skin turns red after exposure to UVA rays. But a large amount of radiation is needed to produce redness.
PPD: The protection factor is measured as a ratio of the dose of UVA radiation is needed to cause an obvious pigmentation of sunscreen-treated skin over the dose needed on unprotected skin.
I mentioned that I prefer to use La Roche Posay Anthelios XL extreme fluide in my previous post.
La Roche Posay uses the PPD-method to make sure their sunblocks are effective in protecting against UVA rays.
They use a special agent called MEXORYL™ SX which is very photostable. MEXORYL™ SX absorbs the UVA rays, deactivates and releases the absorbed energy to the environment as harmless energy, then repeats the process over and over.
Photostability refers to the ability of a molecule to remain intact when exposed to solar radiation.
Several chemical sunscreens degrade and lose their protective value when exposed to solar radiation. For example, avobenzone exhibits up to a 36% loss after 15 minutes of solar simulated light, while octyl methoxycinnamate loses only 4.5%, whereas Mexoryl-SX is especially photostable and silicone-coated zinc oxide is completely photostable.
And this is why I chose La Roche Posay Anthelios sunblock. This may sound like an advertorial but I never get paid for writing this. I am just recommending according to my own experience with the sunblock. I applied it during my Bali holiday trip and I didn’t get sunburnt at all. I turned darker though cos I was too lazy to reapply the sunblock after swimming or some time in the sun. So now I advise all to REAPPLY! =)