How often do you reapply SPF 50 sunscreen?
Irrespective of its SPF number, all sunscreens should be reapplied at least every two hours.
But doesn’t SPF 50 last a lot longer than two hours?
Don’t use the SPF number to indicate how often to reapply the sunscreen.
The 50 in SPF 50 indicates how much protection the sunscreen offers – how much UVB radiation the sunscreen blocks.
The 50 in SPF 50 does not tell us how often to reapply the sunscreen.
How often we reapply sunscreen depends on our skin’s resistance to the sun’s radiation, geographic location and the time of the day.
As a general rule, sunscreen, irrespective of its SPF number, should be reapplied at least every two hours.
So, what does the 50 in SPF 50 measure?
The 50 is a measure of how much UVB radiation the sunscreen blocks.
SPF 50 blocks 98% of the sun’s UVB radiation from affecting the skin. This means SPF 50 allows 2% of the sun’s UVB radiation to enter and affect our skin – the rest it blocks.
Is SPF 50 better than 30?
Yes, SPF 50 is better than SPF 30.
SPF 30 allows 3% of the sun’s UVB radiation to enter and affect our skin.
SPF 50, however, allows 2% of the sun’s UVB radiation to affect our skin.
So, based on these figures, we can say that SPF 30 offers 50% less protection than SPF 50.
The difference between 2% and 3% might not seem much, but when we consider the damage even one additional percent can cause to our skin, the difference suddenly seems high.
What about SPF 15 versus SPF 50?
Yes, SPF 50 is way better than SPF 15.
SPF 15 allows 7% of the sun’s UVB radiation to enter and affect our skin.
SPF 50, however, allows 2% of the sun’s UVB radiation to affect our skin.
So, based on these figures, we can say that SPF 50 offers close to 200% more protection than SPF 15.