Whatever your skincare goals and skin concerns are, one of the most important things to ensure your skin is well maintained and healthy is wearing sunscreen. Here is a comprehensive guide to sunscreens from UVA, UVB, SPF numbers to PA++. Every question you had about sunscreen, answered!
Ultra Violet A
UVA makes up the majority of the UV light that reaches us. Although both UVA and UVB are bad for skin, UVA is more of a threat than UVB. UVA is associated with aging and pigmentation, damages our skin’s genes, and one of the causes of skin cancer. It penetrates deep into the skin layer. Even on a pleasant or a cloudy day, when there is no sun, UVA rays are there. UVA rays even penetrate glass. So your skin is exposed to UVA rays all day, every day.
Ultra Violet B
UVB causes sunburn and redness. Although it does not penetrates the skin, but it can be damaging to the skin. UVB protection is measured by the sun protection factor (SPF). SPF is a better predictor of protection against UVB.
Sunscreen Protection Factor
A sunscreen with SPF 50 will protect the skin until it is exposed to 50 times more UVB radiation than that is required to burn the unprotected skin. The SPF indicates a relative amount of time from sunlight or how long you can stay in direct sunlight before the skin starts to burn.
It is a bit mathematical, but we've got you!
number of minutes when your skin starts burning unprotected sun exposure
SPF rating of your sunscreen
= how long your sun protection will last
For example, if your skin normally changes color after 10 minutes of unprotected sun exposure, so, with SPF 30,
10 minutes x 30 = 300 minutes, which is 5 hours.
So, then you will get five hours of sun protection.
Persistent Pigment Darkening (PPD)
Protection against UVA radiation is measured by the Persistent Pigment Darkening (PPD) Protection Factor. The technique was developed in Japan and has been routinely used by manufacturers but as helpful as it seems, the clinical significance of PPD is not clear. Sunscreens include PA rating, where letters “PA” is followed by plus signs: PA+, PA++, PA+++, and PA++++.
PA+ 2-4 PPD Little UVA protection
PA++ 4-8 PPD Moderate UVA protection
PA+++ 8-16 PPD High UVA protection
PA++++ > 16 PPD Extreme UVA protection
For example, if your skin normally gets tan after 10 minutes of unprotected sun exposure, so with PA++, it will take 4-8x longer.
10 minutes x (4-8) = 40-80 minutes, with full sun protection.
Broad-Spectrum Protection is used to indicate that the product has been tested to claim that it protects from both UVA as well as UVB damage.
An SPF-15 can block 94% of UVB radiation, an SPF-30 can block 97% of UVB radiation while an SPF-50 product will block 98% of UVB radiation. It is recommended to use at least SPF 30, but remember no SPF block 100% of UV rays. To ensure that your skin is well protected from UVA and UVB, look for sunscreens labeled broad spectrum. Therefore, Applying enough sunscreen and reapplying is just as important to protect skin against sun damage.