Thinking about protecting my skin from the sun led me through a few Google searches for product reviews, which also led to some reading on what all those SPFs and UVA-UVB stuff mean. I found them to be pretty informative so I thought I'd share what I learned. :)
- Sunblocks are different from sunscreens. The obvious difference is when applied, sunblocks are more opaque than sunscreens. Sunblocks usually contain ingredients like titanium dioxide which physically block UVB rays. Sunscreen ingredients break down faster when exposed to the sun and need to be reapplied more often.
- SPF stands for Sun Protection Factor and measures the strength of a product against UVB rays (which cause reddening & sunburn). If you're using a sunblock with SPF 50, the amount of UVB rays it takes to burn your skin will need to be 50 times more than that, so you can stay longer under the sun.
- PA stands for Protection Grade UVA and measures the strength of a product against UVA rays (which cause darkening/tanning and can cause cancer). The more pluses next to the PA rating, the longer the protection. The highest I've seen so far is three pluses (PA+++).
- While higher SPF is definitely better, beyond SPF 25 the percentage of UVB rays that you are blocked from is only around 1-2% bigger than the previous SPF, but needs more amounts of sun-blocking chemicals. Of course, the more stuff we apply to the skin, the more potential it has to do harm than good. (To your wallet as well as yourself.) Only purchase the SPF that you will really need from day to day, and simply reapply when in sunnier places like the beach. Reapplying is safer because the sun-blocking ingredients will have broken down after a couple of hours or so after exposure anyway.
- The consistency of any sunblock will tell you that it should be applied well before sun exposure for it to absorb better. Ideally you should apply 1 teaspoon of sunblock to your face. To know how much 1 teaspoon is at a glance, look at your pointy finger and bend it. The length of the finger from the tip 'til the first bend is an (admittedly imperfect) estimate of how much 1 teaspoon is.
- While face powders with SPF are very attractive buys because of the convenience, the thin layer of powder we usually apply and the speed with which it fades from the skin greatly reduces the protection it offers. Applying too much powder will result in a cakey face and an unattractive white cast. So best to still use sunscreen underneath, and think of your powder with SPF as a complementary to it instead.
Of course, nothing will be better in saving you from the sun than staying out of it (even those high SPF sunblocks). If you can, do avoid exposing yourself to the sun's rays from 10 a.m. - 4 p.m., which is when the sun is strongest. :) Hope it helps!